Revert "Get rid of MSVC's __int64"

This reverts commit d63f79325f.

Minecraft.World/AddMushroomIslandLayer.h

@@ -4,6 +4,6 @@
 class AddMushroomIslandLayer : public Layer
 {
 public:
-    AddMushroomIslandLayer(int64_t seedMixup, shared_ptr<Layer> parent);
+    AddMushroomIslandLayer(__int64 seedMixup, shared_ptr<Layer> parent);
     virtual intArray getArea(int xo, int yo, int w, int h);
 };