fix gcc warnings

Common/CreateFile.cpp

Common/GmshRemote.cpp

Common/LuaBindings.cpp

Common/LuaBindings.h

Common/StringUtils.cpp

Fltk/pluginWindow.cpp

Fltk/solverWindow.cpp

Fltk/visibilityWindow.cpp

Geo/Cell.cpp

Geo/Cell.h

Geo/CellComplex.cpp

Geo/ChainComplex.cpp

Geo/GEntity.cpp

Geo/GFaceCompound.cpp

Geo/GModel.cpp

Geo/GModelFactory.cpp

Geo/GModelIO_ACIS.cpp

Geo/GModelIO_Mesh.cpp

Geo/GeomMeshMatcher.cpp

Geo/Homology.cpp