gpac-libgpac needs libglut now

[John Hein]

Li-Wen Hsu wrote at 06:52 +0800 on Feb 18, 2009:
 > Thanks, I am looking into this issue there days, but currently I just
 > don't know why I cannot reproduce this error, and testing in the
 > tinderbox just works fine.  I'll commit the patch if others test this
 > OK.

gpac-libgpac's configure script points to /usr/X11R6 by default.
Possibly it works for some who have a /usr/X11R6 -> /usr/local link.