change management of "ab" option in ffmpeg.c, so that it works as "b" option.

patch by Benoit Fouet % benoit P fouet A purplelabs P com %
Original thread:
Subj: [Ffmpeg-devel] [PATCH] use new way to handle "ab" option
Date: 03/03/2007 10:51 PM

Originally committed as revision 8244 to svn://svn.ffmpeg.org/ffmpeg/trunk