Move Vector2i custom hash to separate header file.

Core/include/Core/v2i_hash.hpp

@@ -0,0 +1,14 @@
+#pragma once
+#include "J3ML/LinearAlgebra/Vector2i.hpp"
+
+using namespace J3ML::LinearAlgebra;
+template<>
+struct std::hash<Vector2i>
+{
+    std::size_t operator()(const Vector2i& k) const
+    {
+        // Read 2x int32_t into one int64_t and return std::hash<int64_t> to prevent collisions.
+        // This doesn't really gain any performance until you zoom out a lot.
+        return std::hash<int64_t>()(((int64_t) k.x << 32) | ((int64_t) k.y));
+    }
+};