Use PNG format for dot images for doxygen documentation
Use PNG format for dot images for doxygen documentation

GIF is less and less supported and in most ways inferior to PNG.

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