Get rid of MSVC's __int64

Use either int64_t, uint64_t or long long and unsigned long long, defined as per C++11 standard

Minecraft.World/IslandLayer.cpp

@@ -1,7 +1,7 @@
 #include "stdafx.h"
 #include "net.minecraft.world.level.newbiome.layer.h"
 
-IslandLayer::IslandLayer(__int64 seedMixup) : Layer(seedMixup)
+IslandLayer::IslandLayer(int64_t seedMixup) : Layer(seedMixup)
 {
 }