Convert a lot of 'int' variables to 'bool'.

My normal habit these days, in new code, is to treat int and bool as
_almost_ completely separate types. I'm still willing to use C's
implicit test for zero on an integer (e.g. 'if (!blob.len)' is fine,
no need to spell it out as blob.len != 0), but generally, if a
variable is going to be conceptually a boolean, I like to declare it
bool and assign to it using 'true' or 'false' rather than 0 or 1.

PuTTY is an exception, because it predates the C99 bool, and I've
stuck to its existing coding style even when adding new code to it.
But it's been annoying me more and more, so now that I've decided C99
bool is an acceptable thing to require from our toolchain in the first
place, here's a quite thorough trawl through the source doing
'boolification'. Many variables and function parameters are now typed
as bool rather than int; many assignments of 0 or 1 to those variables
are now spelled 'true' or 'false'.

I managed this thorough conversion with the help of a custom clang
plugin that I wrote to trawl the AST and apply heuristics to point out
where things might want changing. So I've even managed to do a decent
job on parts of the code I haven't looked at in years!

To make the plugin's work easier, I pushed platform front ends
generally in the direction of using standard 'bool' in preference to
platform-specific boolean types like Windows BOOL or GTK's gboolean;
I've left the platform booleans in places they _have_ to be for the
platform APIs to work right, but variables only used by my own code
have been converted wherever I found them.

In a few places there are int values that look very like booleans in
_most_ of the places they're used, but have a rarely-used third value,
or a distinction between different nonzero values that most users
don't care about. In these cases, I've _removed_ uses of 'true' and
'false' for the return values, to emphasise that there's something
more subtle going on than a simple boolean answer:
 - the 'multisel' field in dialog.h's list box structure, for which
   the GTK front end in particular recognises a difference between 1
   and 2 but nearly everything else treats as boolean
 - the 'urgent' parameter to plug_receive, where 1 vs 2 tells you
   something about the specific location of the urgent pointer, but
   most clients only care about 0 vs 'something nonzero'
 - the return value of wc_match, where -1 indicates a syntax error in
   the wildcard.
 - the return values from SSH-1 RSA-key loading functions, which use
   -1 for 'wrong passphrase' and 0 for all other failures (so any
   caller which already knows it's not loading an _encrypted private_
   key can treat them as boolean)
 - term->esc_query, and the 'query' parameter in toggle_mode in
   terminal.c, which _usually_ hold 0 for ESC[123h or 1 for ESC[?123h,
   but can also hold -1 for some other intervening character that we
   don't support.

In a few places there's an integer that I haven't turned into a bool
even though it really _can_ only take values 0 or 1 (and, as above,
tried to make the call sites consistent in not calling those values
true and false), on the grounds that I thought it would make it more
confusing to imply that the 0 value was in some sense 'negative' or
bad and the 1 positive or good:
 - the return value of plug_accepting uses the POSIXish convention of
   0=success and nonzero=error; I think if I made it bool then I'd
   also want to reverse its sense, and that's a job for a separate
   piece of work.
 - the 'screen' parameter to lineptr() in terminal.c, where 0 and 1
   represent the default and alternate screens. There's no obvious
   reason why one of those should be considered 'true' or 'positive'
   or 'success' - they're just indices - so I've left it as int.

ssh_scp_recv had particularly confusing semantics for its previous int
return value: its call sites used '<= 0' to check for error, but it
never actually returned a negative number, just 0 or 1. Now the
function and its call sites agree that it's a bool.

In a couple of places I've renamed variables called 'ret', because I
don't like that name any more - it's unclear whether it means the
return value (in preparation) for the _containing_ function or the
return value received from a subroutine call, and occasionally I've
accidentally used the same variable for both and introduced a bug. So
where one of those got in my way, I've renamed it to 'toret' or 'retd'
(the latter short for 'returned') in line with my usual modern
practice, but I haven't done a thorough job of finding all of them.

Finally, one amusing side effect of doing this is that I've had to
separate quite a few chained assignments. It used to be perfectly fine
to write 'a = b = c = TRUE' when a,b,c were int and TRUE was just a
the 'true' defined by stdbool.h, that idiom provokes a warning from
gcc: 'suggest parentheses around assignment used as truth value'!

sshshare.c

@@ -160,7 +160,8 @@ struct ssh_sharing_connstate {
 
     int crLine;                        /* coroutine state for share_receive */
 
-    int sent_verstring, got_verstring, curr_packetlen;
+    bool sent_verstring, got_verstring;
+    int curr_packetlen;
 
     unsigned char recvbuf[0x4010];
     int recvlen;
@@ -235,13 +236,13 @@ struct share_channel {
     int x11_auth_proto;
     char *x11_auth_data;
     int x11_auth_datalen;
-    int x11_one_shot;
+    bool x11_one_shot;
 };
 
 struct share_forwarding {
     char *host;
     int port;
-    int active;             /* has the server sent REQUEST_SUCCESS? */
+    bool active;            /* has the server sent REQUEST_SUCCESS? */
     struct ssh_rportfwd *rpf;
 };
 
@@ -263,7 +264,7 @@ struct share_xchannel {
      * channel messages from the server until such time as the server
      * sends us CHANNEL_CLOSE.
      */
-    int live;
+    bool live;
 
     /*
      * When we receive OPEN_CONFIRMATION, we will need to send a
@@ -291,7 +292,7 @@ enum {
 struct share_globreq {
     struct share_globreq *next;
     int type;
-    int want_reply;
+    bool want_reply;
     struct share_forwarding *fwd;
 };
 
@@ -571,7 +572,7 @@ static struct share_channel *share_add_channel
     chan->x11_auth_data = NULL;
     chan->x11_auth_proto = -1;
     chan->x11_auth_datalen = 0;
-    chan->x11_one_shot = 0;
+    chan->x11_one_shot = false;
     if (add234(cs->channels_by_us, chan) != chan) {
         sfree(chan);
         return NULL;
@@ -936,7 +937,7 @@ static void share_disconnect(struct ssh_sharing_connstate *cs,
 }
 
 static void share_closing(Plug *plug, const char *error_msg, int error_code,
-			  int calling_back)
+			  bool calling_back)
 {
     struct ssh_sharing_connstate *cs = container_of(
         plug, struct ssh_sharing_connstate, plug);
@@ -997,7 +998,7 @@ void share_dead_xchannel_respond(struct ssh_sharing_connstate *cs,
      * Handle queued incoming messages from the server destined for an
      * xchannel which is dead (i.e. downstream sent OPEN_FAILURE).
      */
-    int delete = false;
+    bool delete = false;
     while (xc->msghead) {
         struct share_xchannel_message *msg = xc->msghead;
         xc->msghead = msg->next;
@@ -1157,7 +1158,7 @@ void share_setup_x11_channel(ssh_sharing_connstate *cs, share_channel *chan,
         sfree(chan->x11_auth_data);
         chan->x11_auth_proto = -1;
         chan->x11_auth_datalen = 0;
-        chan->x11_one_shot = 0;
+        chan->x11_one_shot = false;
     }
 }
 
@@ -1312,7 +1313,7 @@ static void share_got_pkt_from_downstream(struct ssh_sharing_connstate *cs,
     char *err = NULL;
     BinarySource src[1];
     size_t wantreplypos;
-    int orig_wantreply;
+    bool orig_wantreply;
 
     BinarySource_BARE_INIT(src, pkt, pktlen);
 
@@ -1635,7 +1636,8 @@ static void share_got_pkt_from_downstream(struct ssh_sharing_connstate *cs,
              * a downstream, and if the latter, which one.
              */
             if (ptrlen_eq_string(request_name, "x11-req")) {
-                int want_reply, single_connection, screen;
+                bool want_reply, single_connection;
+                int screen;
                 ptrlen auth_data;
                 int auth_proto;
 
@@ -1844,7 +1846,7 @@ static void share_sent(Plug *plug, int bufsize)
 }
 
 static void share_listen_closing(Plug *plug, const char *error_msg,
-				 int error_code, int calling_back)
+				 int error_code, bool calling_back)
 {
     ssh_sharing_state *sharestate =
         container_of(plug, ssh_sharing_state, plug);
@@ -1968,8 +1970,8 @@ static int share_listen_accepting(Plug *plug,
 
 /* Per-application overrides for what roles we can take (e.g. pscp
  * will never be an upstream) */
-extern const int share_can_be_downstream;
-extern const int share_can_be_upstream;
+extern const bool share_can_be_downstream;
+extern const bool share_can_be_upstream;
 
 /*
  * Decide on the string used to identify the connection point between
@@ -2015,7 +2017,7 @@ char *ssh_share_sockname(const char *host, int port, Conf *conf)
     return sockname;
 }
 
-int ssh_share_test_for_upstream(const char *host, int port, Conf *conf)
+bool ssh_share_test_for_upstream(const char *host, int port, Conf *conf)
 {
     char *sockname, *logtext, *ds_err, *us_err;
     int result;
@@ -2071,7 +2073,8 @@ Socket *ssh_connection_sharing_init(
     const char *host, int port, Conf *conf, LogContext *logctx,
     Plug *sshplug, ssh_sharing_state **state)
 {
-    int result, can_upstream, can_downstream;
+    int result;
+    bool can_upstream, can_downstream;
     char *logtext, *ds_err, *us_err;
     char *sockname;
     Socket *sock, *toret = NULL;