Changed the way the "when" variable is used internally in shutdown.c.

It starts as a NULL pointer, then might get set as a pointer to optarg,
then it might get set to point to an argv parameter, then it might have
a string value copied into it, over-writing the original data. We should
not risk over-writing internal variables which might get used for something
else (it's rude and security risk). Set up "when" as its own buffer
that has data from optargs and/or argv copied into it.

Minor code fixes across multiple source files to avoid buffer
overflows, or uninitialized strings.

src/logsave.c

@@ -282,7 +282,7 @@ int main(int argc, char **argv)
 	outfn = argv[optind];
 	optind++;
 	argv += optind;
-	argc -= optind;
+	/* argc -= optind;  - this is not used */
 
 	outfd = open(outfn, openflags, 0644);
 	do_stdin = !strcmp(argv[0], "-");