Add support for default of multiple video tracks.

Some container formats like matroska support multiple video tracks, one
of which may be flagged the 'default' one which thus should be played by
default.

Works with the lavf demuxer.


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36778 b3059339-0415-0410-9bf9-f77b7e298cf2
Improve emphasizing of the current video track.

This is correspondent with r34643 (audio tracks).


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36779 b3059339-0415-0410-9bf9-f77b7e298cf2
Rename the Danish messages header file.

There is no ISO 639-1 language code "dk", Danish is "da".


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36780 b3059339-0415-0410-9bf9-f77b7e298cf2