WGL_EXT_make_current_read
http://www.opengl.org/registry/specs/EXT/wgl_make_current_read.txt
	HDC wglGetCurrentReadDCEXT (VOID)
	BOOL wglMakeContextCurrentEXT (HDC hDrawDC, HDC hReadDC, HGLRC hglrc)
	ERROR_INVALID_PIXEL_TYPE_EXT 0x2043
