avg_splineedit: Added ability to remove a control point.
avg_splineedit: Added ability to remove a control point.

svn path=/trunk/libavg/; revision=7063

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