* Improve avformat demux SET_POSITION.
* Add WavPack ID for ffmpeg demux
* Add Speex ID for avi files

* check whether p_item->input.psz_name exists, because stringWith*String crashes on non-existant strings

* backport [17543] : Fix mpeg2 PTS/DTS for field pictures

  Attach the Callback before setting the value, if you depend on information being properly set by that callback

 * skins2/parser/skin_parser.cpp: Fixed a crash due to incomplete backports. Also fixed another problem of the same kind.

* Don't skip the Real RTSP access if it is NOT forced. (apparently b_force was broken before or something ? )
  This fixes #821

* implement the playmode buttons and the fullscreen panel. TODO: fix mainmenu.nib (bring back the old-school error panel), fix some compilation warnings, make sure that the fspanel is hidden on vout:close. Any other remarks are appreciated.

* add the necessary graphics for the fullscreen panel and the playmode buttons. Implementation files follow later on

Closes #815