Reuse handleSelection instead of manual position computing
Reuse handleSelection instead of manual position computing

This will allow the TreeView to properly hook into clicks and open/close
its nodes subtrees.

cbeck88/cegui-mirror,arkana-fts/cegui,arkana-fts/cegui,cbeck88/cegui-mirror,arkana-fts/cegui,RealityFactory/CEGUI,RealityFactory/CEGUI,arkana-fts/cegui,cbeck88/cegui-mirror,RealityFactory/CEGUI,RealityFactory/CEGUI,arkana-fts/cegui,cbeck88/cegui-mirror,cbeck88/cegui-mirror,RealityFactory/CEGUI