Cast pid_t to long for fprintf()

pid_t is defined by POSIX to be a signed integer type, so the %u format is wrong.

Cast to long and print with %ld - it is unlikely that any real-world system has pid_t bigger than long.

source/irc.c

@@ -1434,7 +1434,7 @@ pid_t pid;
 		unlink(pidfile);
 		if ((t = fopen(pidfile, "w")))
 		{
-			fprintf(t, "%u\n", pid);
+			fprintf(t, "%ld\n", (long)pid);
 			fclose(t);
 		}
 	}