FIX: Ensure Window target surfaces are in sync when setting GUIContext.
FIX: Ensure Window target surfaces are in sync when setting GUIContext.

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