MediaPlayer macOS 10.13 Beta 2 to Beta 3 API Differences

MediaPlayerDefines.h
Removed #def MP_EXTERN_CLASS
Removed #def MP_EXTERN_CLASS_AVAILABLE
Removed #def MP_EXTERN_CLASS_AVAILABLE_X
Removed #def MP_API_IOS_AVAILABLE_TVOS_PROHIBITED
Removed #def MP_API_IOS_AVAILABLE_MACOS_TVOS_PROHIBITED
Removed #def MP_API_IOS_DEPRECATED_TVOS_PROHIBITED
Removed #def MP_API_IOS_DEPRECATED_MACOS_TVOS_PROHIBITED
Removed #def MP_API_IOS_DEPRECATED_WITH_REPLACEMENT_MACOS_TVOS_PROHIBITED
Added #def MP_PROHIBITED
MPError.h
MPMediaItem.h
MPRemoteCommand.h