Workaround render glitches on new MacBooks.

For unknown reason large windows have bad render glitches in High Sierra.
Forcing of OpenGL composition (by adding a fake child QOpenGLWidget) fixes it.

Telegram/SourceFiles/window/main_window.cpp

@@ -135,6 +135,9 @@ void MainWindow::updateWindowIcon() {
 }
 
 void MainWindow::init() {
+	Expects(!windowHandle());
+	createWinId();
+
 	initHook();
 	updateWindowIcon();