- my mistake... mpeg2dec libs does not depend on X11 libraries (vo library distribute...

- my mistake... mpeg2dec libs does not depend on X11 libraries (vo library distributed with mpeg2dec depends on X11 l...

Original commit message from CVS:
- my mistake... mpeg2dec libs does not depend on X11 libraries
(vo library distributed with mpeg2dec depends on X11 libs).
Add configure option so user can specify where mpeg2dec library
is installed. This way we do not guess where is mpeg2dec.
If it is not in standard location (prefix==/usr), then leave it
to the user.
Changes inspired by AM_PATH_LIBMIKMOD.