Don't use Windows.h in WindowsWrapper.h

The need for this was eliminates ages ago, when I remove the
WindowsWrapper.h dependencies from the backends (it should only be
used by core Cave Story code).

This should eliminate any future issues with Windows.h causing
name-collisions.

src/WindowsWrapper.h

@@ -1,12 +1,5 @@
 #pragma once
 
-#ifdef _WIN32
-#define WIN32_LEAN_AND_MEAN
-#define NODRAWTEXT
-#include <windows.h>
-#undef FindResource
-#else
-
 #define RGB(r,g,b) ((r) | ((g) << 8) | ((b) << 16))
 
 typedef bool BOOL;
@@ -21,5 +14,3 @@ struct RECT
 	long right;
 	long bottom;
 };
-
-#endif