Integer conversion fixes

Fltk/visibilityWindow.cpp

Geo/MElementCut.cpp

Geo/MElementOctree.cpp

Geo/MVertex.h

Graphics/drawMesh.cpp

Mesh/BackgroundMesh2D.cpp

Mesh/QuadTriExtruded2D.cpp

Mesh/ThinLayer.cpp

Mesh/Voronoi3D.cpp

Mesh/directions3D.cpp

Mesh/meshPartition.cpp

Mesh/meshRefine.cpp

Mesh/simple3D.cpp

Mesh/surfaceFiller.cpp

Mesh/yamakawa.cpp

Plugin/Crack.cpp

Plugin/Distance.cpp

Plugin/FaultZone.cpp

Plugin/FieldFromAmplitudePhase.cpp

Plugin/ShowNeighborElements.cpp