Acknowledge in-app purchases to avoid auto-refund.

This update from Apple will improve the functionality of this app. No new features are included.

→ Online matchmaking now via Game Center.
→ New online arenas.

→ Replaced GameCenter multiplayer with custom game server.
→ Added support for iOS vs other OSes multi player.
→ Unified code bases.

→ Fix iPhone5S crash when ending level. (discardFramebufferEXT before present)
→ Built against iOS7 SDK.

- New premium level 'fortress'
- Fixed hanging sound after opponent disconnect.

* Fixed crash in matchmakerViewController:didFindMatch:
* Fixed friend invites.
* Disabled region segregation for larger player pool.