fixed g++ warnings

Common/CommandLine.cpp

Common/Options.cpp

Fltk/Callbacks.cpp

Fltk/GUI.cpp

Fltk/GUI_Classifier.cpp

Fltk/GUI_Projection.cpp

Fltk/Solvers.cpp

Geo/GFace.cpp

Geo/Geo.cpp

Graphics/Geom.cpp

Graphics/Graph2D.cpp

Graphics/Post.cpp

Mesh/Field.cpp

Mesh/meshGEdge.cpp

Mesh/meshGFace.cpp

Parser/OpenFile.cpp

Plugin/CutMap.cpp

Plugin/Evaluate.cpp

Plugin/ExtractEdges.cpp

Plugin/FieldView.cpp