Properly pause all audio processing in Android when minimized.

This uses ALC_SOFT_pause_device extension which is available since
OpenAL-soft 1.16. We guarantee almost 100% availability of this extension
since we've been using OpenAL-soft in Android since beginning.

Fixes #1828

src/modules/event/sdl/Event.h

@@ -78,10 +78,6 @@ private:
 	static std::map<SDL_Keycode, love::keyboard::Keyboard::Key> createKeyMap();
 	static std::map<SDL_Keycode, love::keyboard::Keyboard::Key> keys;
 
-#ifdef LOVE_ANDROID
-	std::vector<love::audio::Source*> pausedSources;
-#endif
-
 }; // Event
 
 } // sdl