Disable the GUI on exit for XBMC

[TheDax]

Should be fixed if/when https://github.com/hrydgard/ppsspp/pull/5838 is merged. It should be fixed now. Grab the newest git build once it's up. Also, it's not really as simple as never showing the in-window GUI, since the majority of the settings are actually in there, and not in the Windows menu bar. Most of them used to be in the menu bar, but it got so cluttered that it took forever to find anything. It made more sense to have a more settings option and use your mouse + mouse wheel (or controller/keyboard, either way) to find what you need quickly. If we had an option to let the user disable the in-window GUI entirely, we'd probably get "bug reports" that the screen is only black until they select a game, or when they press escape to try and change settings. Also, the GUI runs on the same thread as the emulation itself (hence why the game pauses when you go back into the in-window menus), so it's still not so easy to just disable that and only run the emulation.