changed VIDEOPLAYER_SUBTITLES_LANG number to 309
Adapt DVDFileInfo so that it reads the language from external subtitles files.
TODO: Split up

- add VideoPlayer.AudioLanguage infolabel that returns full language name of current subtitles, "unknown" localized string or empty string if subtitles are disabled or video isn't playing currently

- use 3 char code

- add language recognition for external audio files to DVDFileInfo

- add language recognition for external audio files to DVDPlayer