FIX: GL3 renderer was relying on function not available in 3.2 core profile.
FIX: GL3 renderer was relying on function not available in 3.2 core profile.

ruleless/CEGUI,ruleless/CEGUI,OpenTechEngine/CEGUI,OpenTechEngine/CEGUI,ruleless/CEGUI,OpenTechEngine/CEGUI,ruleless/CEGUI,OpenTechEngine/CEGUI