Make lots of generic data parameters into 'void *'.

This is a cleanup I started to notice a need for during the BinarySink
work. It removes a lot of faffing about casting things to char * or
unsigned char * so that some API will accept them, even though lots of
such APIs really take a plain 'block of raw binary data' argument and
don't care what C thinks the signedness of that data might be - they
may well reinterpret it back and forth internally.

So I've tried to arrange for all the function call APIs that ought to
have a void * (or const void *) to have one, and those that need to do
pointer arithmetic on the parameter internally can cast it back at the
top of the function. That saves endless ad-hoc casts at the call
sites.

unix/gtkwin.c

@@ -304,13 +304,13 @@ char *get_ttymode(void *frontend, const char *mode)
     return term_get_ttymode(inst->term, mode);
 }
 
-int from_backend(void *frontend, int is_stderr, const char *data, int len)
+int from_backend(void *frontend, int is_stderr, const void *data, int len)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
     return term_data(inst->term, is_stderr, data, len);
 }
 
-int from_backend_untrusted(void *frontend, const char *data, int len)
+int from_backend_untrusted(void *frontend, const void *data, int len)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
     return term_data_untrusted(inst->term, data, len);

unix/uxnet.c

@@ -509,8 +509,8 @@ static void sk_tcp_flush(Socket s)
 }
 
 static void sk_tcp_close(Socket s);
-static int sk_tcp_write(Socket s, const char *data, int len);
-static int sk_tcp_write_oob(Socket s, const char *data, int len);
+static int sk_tcp_write(Socket s, const void *data, int len);
+static int sk_tcp_write_oob(Socket s, const void *data, int len);
 static void sk_tcp_write_eof(Socket s);
 static void sk_tcp_set_frozen(Socket s, int is_frozen);
 static char *sk_tcp_peer_info(Socket s);
@@ -1189,7 +1189,7 @@ void try_send(Actual_Socket s)
     uxsel_tell(s);
 }
 
-static int sk_tcp_write(Socket sock, const char *buf, int len)
+static int sk_tcp_write(Socket sock, const void *buf, int len)
 {
     Actual_Socket s = (Actual_Socket) sock;
 
@@ -1215,7 +1215,7 @@ static int sk_tcp_write(Socket sock, const char *buf, int len)
     return bufchain_size(&s->output_data);
 }
 
-static int sk_tcp_write_oob(Socket sock, const char *buf, int len)
+static int sk_tcp_write_oob(Socket sock, const void *buf, int len)
 {
     Actual_Socket s = (Actual_Socket) sock;
 

unix/uxpgnt.c

@@ -93,7 +93,7 @@ FontSpec *platform_default_fontspec(const char *name) { return fontspec_new("");
 Filename *platform_default_filename(const char *name) { return filename_from_str(""); }
 char *x_get_default(const char *key) { return NULL; }
 void log_eventlog(void *handle, const char *event) {}
-int from_backend(void *frontend, int is_stderr, const char *data, int datalen)
+int from_backend(void *frontend, int is_stderr, const void *data, int datalen)
 { assert(!"only here to satisfy notional call from backend_socket_log"); }
 
 /*
@@ -156,7 +156,8 @@ static int time_to_die = FALSE;
  * used, because in LIFE_X11 mode we connect to the X server using a
  * straightforward Socket and don't try to create an ersatz SSH
  * forwarding too. */
-int sshfwd_write(struct ssh_channel *c, char *data, int len) { return 0; }
+int sshfwd_write(struct ssh_channel *c, const void *data, int len)
+{ return 0; }
 void sshfwd_write_eof(struct ssh_channel *c) { }
 void sshfwd_unclean_close(struct ssh_channel *c, const char *err) { }
 void sshfwd_unthrottle(struct ssh_channel *c, int bufsize) {}

unix/uxplink.c

@@ -402,7 +402,7 @@ int try_output(int is_stderr)
 }
 
 int from_backend(void *frontend_handle, int is_stderr,
-		 const char *data, int len)
+                 const void *data, int len)
 {
     if (is_stderr) {
 	bufchain_add(&stderr_data, data, len);
@@ -414,7 +414,7 @@ int from_backend(void *frontend_handle, int is_stderr,
     }
 }
 
-int from_backend_untrusted(void *frontend_handle, const char *data, int len)
+int from_backend_untrusted(void *frontend_handle, const void *data, int len)
 {
     /*
      * No "untrusted" output should get here (the way the code is

unix/uxproxy.c

@@ -175,7 +175,7 @@ static int localproxy_try_send(Local_Proxy_Socket ps)
     return sent;
 }
 
-static int sk_localproxy_write (Socket s, const char *data, int len)
+static int sk_localproxy_write (Socket s, const void *data, int len)
 {
     Local_Proxy_Socket ps = (Local_Proxy_Socket) s;
 
@@ -188,7 +188,7 @@ static int sk_localproxy_write (Socket s, const char *data, int len)
     return bufchain_size(&ps->pending_output_data);
 }
 
-static int sk_localproxy_write_oob (Socket s, const char *data, int len)
+static int sk_localproxy_write_oob (Socket s, const void *data, int len)
 {
     /*
      * oob data is treated as inband; nasty, but nothing really