Ports: Replace mc config.sub patch with our own download

`mc` runs `autoconf` on the fly, which unpacks a `config.sub` from its
own files. This means that support for `serenity` (and the fact whether
the patch successfully applies) depends on the version of `autoconf`
that is installed on the host.

Instead, just always replace it with a fresh version straight from the
GNU server.

Ports/mc/patches/0001-filemanager-ext.c-Include-strings.h-if-SerenityOS.patch

@@ -0,0 +1,30 @@
+From 749c81e5006dea41daf16e99c8a60926236d2373 Mon Sep 17 00:00:00 2001
+From: Kenneth Myhra <kennethmyhra@gmail.com>
+Date: Sat, 25 Dec 2021 19:15:35 +0100
+Subject: [PATCH 1/2] filemanager/ext.c: Include strings.h if SerenityOS
+
+- [ ] Local?
+- [X] Should be merged to upstream?
+- [ ] Resolves issue(s) with our side of things
+- [ ] Hack
+---
+ src/filemanager/ext.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/src/filemanager/ext.c b/src/filemanager/ext.c
+index 781a763..33baf8c 100644
+--- a/src/filemanager/ext.c
++++ b/src/filemanager/ext.c
+@@ -36,6 +36,9 @@
+ #include <stdlib.h>
+ #include <stdio.h>
+ #include <string.h>
++#ifdef __serenity__
++#include <strings.h>
++#endif
+ #include <unistd.h>
+ 
+ #include "lib/global.h"
+-- 
+2.25.1
+