Fix incorrect pgc_t ordering
libdvdread currently has (in pgc_t in ifo_types.h) still_time before pg_playback_mode.
This is what is described at http://dvd.sourceforge.net/dvdinfo/pgc.html with the two members at offset 0xa2 and 0xa3 within the PGC respectively.
Currently libdvdnav doesn't support random playback mode, but I have a patch for that too which will add it in, because I have some disks which use random play mode as part of their copy-protection and will not play unless those fields are correctly read, interpreted, and implemented. And that patch requires that it be fed the correct value by libdvdread.
(I wonder if that's also related to the comment in libdvdnav/src/vm/vm.c:vm_position_get()...)