Under linux, force libsdl to use X11 video backend, improved error message if video init fails. Fixes #417.
Under linux, force libsdl to use X11 video backend, improved error message if video init fails. Fixes #417.

svn path=/trunk/libavg/; revision=9252

scotty007/libavg,yyd01245/libavg,hoodie/libavg,libavg/libavg,th3infinity/libavg,yyd01245/libavg,libavg/libavg,yyd01245/libavg,th3infinity/libavg,hoodie/libavg,libavg/libavg,scotty007/libavg,yyd01245/libavg,scotty007/libavg,hoodie/libavg,th3infinity/libavg,hoodie/libavg,scotty007/libavg,libavg/libavg,th3infinity/libavg