[GL] Forward declarations instead of including.

Applications/DataExplorer/DataView/GEOModels.cpp

Applications/DataExplorer/DataView/GeoTreeModel.cpp

Applications/DataExplorer/VtkVis/VtkSurfacesSource.cpp

Applications/Utils/FileConverter/generateBCandGLI.cpp

FileIO/TetGenInterface.cpp

FileIO/XmlIO/Qt/XmlGmlInterface.cpp

GeoLib/GEOObjects.cpp

GeoLib/Raster.cpp

GeoLib/Surface.cpp

GeoLib/Surface.h

MeshLib/convertMeshToGeo.cpp

Tests/FileIO/TestXmlGmlReader.cpp