* Rename UC_OSX (and related constants) to UC_MAC
* Update UNICODE_SONG_OSX references to UNICODE_SONG_MAC
* Update UC_M_OS references to UC_M_MA
* Add UC_OSX alias for backwards compatibility
* Add deprecation warning for UC_OSX to Unicode docs
* Add UC_M_OS alias for backwards compatibility
* Update newly found UC_M_OS and UNICODE_SONG_OSX references
* Add legacy UNICODE_MODE_OSX alias, revert changes to user keymaps
* Add legacy UNICODE_SONG_OSX alias, revert changes to user keymaps
* Replace removed sounds in Unicode song doc examples