1 - Fixed memory leak in MRC: (had forgotten to write KVOContext dealloc)
2 - Fixed memory leak in ARC: (was purposedly not calling original dealloc implementation on NSObject in ARC, because some Xcode projects would crash when doing so... might need to look further into this. )
3 - Replaced the code that would explictly copy the callback block by copy qualifier in @property declaration.
4 - -dealloc for KVOContext and KVOProxy is now conditionally compiled or left out as a whole, instead of just the release of their members.
5 - Corrected a harmless naming typo.