Added libswscale dependency check to configure.
Added libswscale dependency check to configure.

svn path=/trunk/libavg/; revision=3460

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