fix compile warnings

Fltk/fileDialogs.cpp

Fltk/graphicWindow.cpp

Geo/GModel.cpp

Mesh/Generator.cpp

Mesh/delaunay3d.cpp

Mesh/delaunay3d.h

Mesh/delaunay_refinement.cpp

Mesh/delaunay_refinement.h

Mesh/qualityMeasuresJacobian.cpp

Mesh/simple3D.cpp

Numeric/MetricBasis.cpp

Parser/Gmsh.tab.cpp

Parser/Gmsh.y

Plugin/ThinLayerFixMesh.cpp