ENGINES: Use common GFX code for 3D games - fixes part of bug #14342

Now, when the launcher is in full screen, the game will also be in full
screen. However, when returning to the launcher, graphics are reset to
default with a setupGraphics() call. Thus, if the user hasn't selected
full screen display in the options, but only used alt-enter to change
the launcher to full screen, the launcher will return to window mode.

initCommonGFX() also applies the following to 3D games:
- Filtering mode
- Sets the scaler
- Sets the shader

engines/engine.cpp

@@ -486,11 +486,8 @@ void initGraphics(int width, int height) {
 void initGraphics3d(int width, int height) {
 	g_system->beginGFXTransaction();
 		g_system->setGraphicsMode(0, OSystem::kGfxModeRender3d);
+		initCommonGFX();
 		g_system->initSize(width, height);
-		g_system->setFeatureState(OSystem::kFeatureFullscreenMode, ConfMan.getBool("fullscreen")); // TODO: Replace this with initCommonGFX()
-		g_system->setFeatureState(OSystem::kFeatureAspectRatioCorrection, ConfMan.getBool("aspect_ratio")); // TODO: Replace this with initCommonGFX()
-		g_system->setFeatureState(OSystem::kFeatureVSync, ConfMan.getBool("vsync")); // TODO: Replace this with initCommonGFX()
-		g_system->setStretchMode(ConfMan.get("stretch_mode").c_str()); // TODO: Replace this with initCommonGFX()
 	g_system->endGFXTransaction();
 
 	if (!splash && !GUI::GuiManager::instance()._launched) {