VideoCommon: keep a copy of the const buffer in VideoCommon

The upload in the backend isn't done, it's just pushed by the mostly removed SetMulti*SConstant4fv.
Also no optimizations was done on VideoCommon side, but I can start now :-)

Sorry for the hacky way, but I think this is a nice (working) snapshot for a much bigger change.

Source/Core/VideoCommon/Src/VertexShaderManager.h

@@ -6,6 +6,7 @@
 #define _VERTEXSHADERMANAGER_H
 
 #include "VertexShaderGen.h"
+#include "ConstantManager.h"
 
 class PointerWrap;
 
@@ -35,6 +36,9 @@ public:
 	static void TranslateView(float x, float y, float z = 0.0f);
 	static void RotateView(float x, float y);
 	static void ResetView();
+	
+	static VertexShaderConstants constants;
+	static bool dirty;
 };
 
 #endif // _VERTEXSHADERMANAGER_H