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

svn path=/trunk/libavg/; revision=7062

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