Add support for Android 2.3+

There have been plenty of ppl involved in creating this version.
I don't wanna mention names as I'm sure I'd forget someone so I
just tell where help has been done:
- The partial android versions done by various ppl
- Testing on different android devices
- reviewing code (especially the in core changes)
- testing controls
- reviewing texts

A big thank you to everyone helping this to be completed!

src/mainmenumanager.h

@@ -124,13 +124,17 @@ public:
 		disconnect_requested(false),
 		changepassword_requested(false),
 		changevolume_requested(false),
+		shutdown_requested(false),
 		device(a_device)
 	{
 	}
 
 	virtual void exitToOS()
 	{
+		shutdown_requested = true;
+#ifndef __ANDROID__
 		device->closeDevice();
+#endif
 	}
 
 	virtual void disconnect()
@@ -151,6 +155,7 @@ public:
 	bool disconnect_requested;
 	bool changepassword_requested;
 	bool changevolume_requested;
+	bool shutdown_requested;
 	IrrlichtDevice *device;
 };