/* Vsync control under Windows.  Checking glGetString here is
	 * somewhat a documented and reliable hack - it was originally
	 * as a feature added by mistake, but since so many people rely
	 * on it, it will not be removed.  strstr should be safe here.*/
	glGetStringFunc = WIN_GL_GetProcAddress(this, "glGetString");
	if ( glGetStringFunc ) {
		wglext = (const char *)glGetStringFunc(GL_EXTENSIONS);
	} else {
		/* Uh oh, something is seriously wrong here... */
		wglext = NULL;
	}
	if ( wglext && SDL_strstr(wglext, "WGL_EXT_swap_control") ) {
		this->gl_data->wglSwapIntervalEXT = WIN_GL_GetProcAddress(this, "wglSwapIntervalEXT");
		this->gl_data->wglGetSwapIntervalEXT = WIN_GL_GetProcAddress(this, "wglGetSwapIntervalEXT");
	} else {
		this->gl_data->wglSwapIntervalEXT = NULL;
		this->gl_data->wglGetSwapIntervalEXT = NULL;
	}
	if ( this->gl_config.swap_control >= 0 ) {
		if ( this->gl_data->wglSwapIntervalEXT ) {
			this->gl_data->wglSwapIntervalEXT(this->gl_config.swap_control);
		}
	}