Bump package version to 20200215

The actual most recent version is 20200215, so update the package version to this.
Furthermore, update the patch accordingly so it still builds. This adds back the
reallocarray.c file.

pkgs/applications/editors/mg/default.nix

@@ -1,12 +1,14 @@
-{ stdenv, fetchurl, pkgconfig, ncurses, buildPackages, libbsd }:
+{ stdenv, fetchFromGitHub, pkgconfig, ncurses, buildPackages, libbsd }:
 
 stdenv.mkDerivation rec {
   pname = "mg";
-  version = "20180927";
+  version = "20200215";
 
-  src = fetchurl {
-    url = "https://github.com/hboetes/mg/archive/${version}.tar.gz";
-    sha256 = "fbb09729ea00fe42dcdbc96ac7fc1d2b89eac651dec49e4e7af52fad4f5788f6";
+  src = fetchFromGitHub {
+    owner = "hboetes";
+    repo = "mg";
+    rev = "20200215";
+    sha256 = "1rss7d43hbq43n63gxfvx4b2vh2km58cchwzdf2ssqhaz3qj40m6";
   };
 
   enableParallelBuilding = true;