minetest: update to 5.1.0 and build on Darwin

pkgs/games/minetest/fix_wordsize_confusion.patch

@@ -0,0 +1,10 @@
+--- a/src/main.cpp
++++ b/src/main.cpp
+@@ -17,6 +17,7 @@
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+ 
++#include <cstdint>
+ #include "irrlicht.h" // createDevice
+ #include "irrlichttypes_extrabloated.h"
+ #include "chat_interface.h"