Fix format string mistakes revealed by new checking.

An assortment of errors: int vs size_t confusion (probably undetected
since the big switchover in commit 0cda34c6f), some outright spurious
parameters after the format string (copy-paste errors), a particularly
silly one in pscp.c (a comma between two halves of what should have
been a single string literal), and a _missing_ format string in ssh.c
(but luckily in a context where the only text that would be wrongly
treated as a format string was error messages generated elsewhere in
PuTTY).

ssh.c

@@ -562,7 +562,7 @@ void ssh_deferred_abort_callback(void *vctx)
     Ssh *ssh = (Ssh *)vctx;
     char *msg = ssh->deferred_abort_message;
     ssh->deferred_abort_message = NULL;
-    ssh_sw_abort(ssh, msg);
+    ssh_sw_abort(ssh, "%s", msg);
     sfree(msg);
 }