Revert "Get rid of MSVC's __int64"

This reverts commit d63f79325f.

Minecraft.World/AddIslandLayer.h

@@ -5,7 +5,7 @@
 class AddIslandLayer : public Layer
 {
 public:
-	AddIslandLayer(int64_t seedMixup, shared_ptr<Layer>parent);
+	AddIslandLayer(__int64 seedMixup, shared_ptr<Layer>parent);
 
 	intArray getArea(int xo, int yo, int w, int h);
 };