OPENGLSDL: Make fullscreen mode switching work again.

backends/graphics/openglsdl/openglsdl-graphics.cpp

@@ -460,6 +460,10 @@ void OpenGLSdlGraphicsManager::toggleFullScreen(int loop) {
 			_activeFullscreenMode = -2;
 			setFullscreenMode(!isFullscreen);
 		}
+
+		// HACK: We need to force a refresh here, since we change the
+		// fullscreen mode.
+		_transactionDetails.needRefresh = true;
 	endGFXTransaction();
 
 	// Ignore resize events for the next 10 frames