Introduce a new utility function smemclr(), which memsets things to

zero but does it in such a way that over-clever compilers hopefully
won't helpfully optimise the call away if you do it just before
freeing something or letting it go out of scope. Use this for
(hopefully) every memset whose job is to destroy sensitive data that
might otherwise be left lying around in the process's memory.

[originally from svn r9586]

unix/gtkwin.c

@@ -3582,7 +3582,7 @@ int pt_main(int argc, char **argv)
     if (argc > 1 && !strncmp(argv[1], "---", 3)) {
 	read_dupsession_data(inst, inst->conf, argv[1]);
 	/* Splatter this argument so it doesn't clutter a ps listing */
-	memset(argv[1], 0, strlen(argv[1]));
+	smemclr(argv[1], strlen(argv[1]));
     } else {
 	/* By default, we bring up the config dialog, rather than launching
 	 * a session. This gets set to TRUE if something happens to change