Give every printf-like function restrict qualifiers

The format value has to be a string literal, every time.

Otherwise, you are not using these functions correctly. To reinforce this fact, I putrestrict over every non-contrib example of this I could find.

src/parse_args.c

@@ -760,7 +760,7 @@ usage_excl_ticket(void)
 }
 
 static int
-help_out(const char *buf)
+help_out(const char * restrict buf)
 {
     return fputs(buf, stdout);
 }