Ports: Update genemu's patches to use git patches

This required splitting the single patch file up, which was done with
_some_ degree of accuracy (but not entirely so).

Ports/genemu/patches/0003-Add-a-missing-cstdlib-include.patch

@@ -0,0 +1,24 @@
+From 0c4abad4174c3b12d5a42b62a47718896961610a Mon Sep 17 00:00:00 2001
+From: aabajyan <arsen.abajyan@pm.me>
+Date: Sun, 7 Mar 2021 22:30:13 +0400
+Subject: [PATCH 3/5] Add a missing cstdlib include
+
+---
+ mem.cpp | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/mem.cpp b/mem.cpp
+index fd36d68..4cf0b30 100644
+--- a/mem.cpp
++++ b/mem.cpp
+@@ -10,6 +10,7 @@ extern "C" {
+ #include "vdp.h"
+ #include "cpu.h"
+ #include "ioports.h"
++#include <cstdlib>
+ 
+ uint8_t *ROM;
+ uint8_t RAM[0x10000];
+-- 
+2.36.1
+