Updates for show single frame.

- allow h264 still images to be shown (based on showiframe patch from
  Erik slagter)
- vusolo2 (and probably dus2 too) did not properly show single
  iframes in enigma2 with drivers from before 2013. This was very
  noticable when in radio mode.
fix typo in decoder.cpp

Thanks IMS
bg.po: translation updates by marto
GraphMultiEpg: Change zap behaviour in GMEPG

Only quit GMEPG when you zap to the current played channel. This will
lead to the effect that during normal zapping the GMEPG is not quited. It
will quit only when you select 2 x the same channel.
GraphMultiEPG: Fix for previous commit regards alternatives

The reference could be an alternative, so compare for the
alternative.
GraphMultiEPG: More fixes regards alternatives
Merge branch 'master' of git://openpli.git.sourceforge.net/gitroot/openpli/enigma2