Add HDC & hInstance to windows SysWMinfo struct (#494)
Add HDC & hInstance to windows SysWMinfo struct (#494)

https://github.com/libsdl-org/SDL/blob/main/include/SDL_syswm.h#L231 SDL
includes HWND, HDC, and HINSTANCE in the windows-related SysWMinfo
structure.  These are useful values if you have occasion to open up the
guts and do something inadvisable & it would be nice if htey were
available
veandco/go-sdl2,veandco/go-sdl2