Fix mingw64 build: convert from LPVOID to DWORD losses precision on 64-bit platform.
fix mingw32/mingw64 build: use system libs and includes rather than prebuilt ones.
Merge branch 'mingw-build' of github.com:John-He-928/cocos2d-x into mingw-build
Merge pull request #6916 from John-He-928/mingw-build

Fix mingw64 build: convert from LPVOID to DWORD losses precision on 64-b...