Fixed an issue in ExceptionUtils.m reported by Xcode 5.1
Added ARC-compatibility utilities and file-error utility methods.

MYRetain, MYRelease, MYAutorelease
-[NSError my_isFileExistsError]
-[NSError my_isFileNotFoundError]
Removed some obsolete build settings from the xcconfig file
Merge branch 'master' of git://github.com/snej/MYUtilities