When giving authorisation errors from the proxy code in x11fwd.c,

name the proxy using the global 'appname' variable, instead of
statically calling it PuTTY.

(Knock-on effect is that PSCP and PSFTP have to declare that
variable, though of course they shouldn't ever actually _use_ the X
forwarding code. Probably I ought to replace it with a stub
nox11fwd.c for those applications.)

[originally from svn r8501]

pscp.c

@@ -50,6 +50,8 @@ static void source(char *src);
 static void rsource(char *src);
 static void sink(char *targ, char *src);
 
+const char *const appname = "PSCP";
+
 /*
  * The maximum amount of queued data we accept before we stop and
  * wait for the server to process some.

psftp.c

@@ -16,6 +16,8 @@
 #include "sftp.h"
 #include "int64.h"
 
+const char *const appname = "PSFTP";
+
 /*
  * Since SFTP is a request-response oriented protocol, it requires
  * no buffer management: when we send data, we stop and wait for an

x11fwd.c

@@ -712,7 +712,7 @@ int x11_send(Socket s, char *data, int len)
 	    int msglen, msgsize;
 	    unsigned char *reply;
 
-	    message = dupprintf("PuTTY X11 proxy: %s", err);
+	    message = dupprintf("%s X11 proxy: %s", appname, err);
 	    msglen = strlen(message);
 	    reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
 	    msgsize = (msglen + 3) & ~3;