(set codec to xvid if the hanlder is xvid).

* modules/demux/mp4/*: fixed segfault on close with some files.

* src/video_output/video_output.c: make sure vout_Create() returns NULL when the pf_init() of the vout plugin failed.

* make sure the terminate of the super is called

This might fix the CodeTek VirtualDesktop appl. (untested)

            DoExtShuffle into smaller functions.

   I didn't remove all the code handling the removed attribute (Playlist.var),
   because it can still be useful if we decide to have other List controls.

                              widths (MMX untested)

                   in window mode. I'm not sure how we can catch
                   mouseDown events in fullscreen GL mode)