-Fall back to one-packet-once reading in dvd input since multi-block

-Fall back to one-packet-once reading in dvd input since multi-block
seems to have a bug that make the vlc crash on title/audio/spu change. I
hope that this bug will be fixed soon for the performance is poorer now

-add-ons and changes in gnome interface:
        *menu subdivision is done only if there are over 20 items,
        *in DVD mode next/prev apply to title,
        *in DVD mode, added a box with button to navigate through
         chapters.
This has not been finished yet (and it is not in gtk plugin then). And I
think I will leave toolbar next/prev buttons for playlist and add
button specifically for title change like for chapters.*