add voro++ and rtree

CMakeLists.txt

Common/GmshConfig.h.in

Geo/GFaceCompound.cpp

Mesh/CMakeLists.txt

Mesh/Levy3D.cpp

Mesh/Levy3D.h

Mesh/Voronoi3D.cpp

Mesh/Voronoi3D.h

Mesh/meshGFaceLloyd.cpp

Mesh/meshGFaceLloyd.h

Mesh/meshGRegion.cpp

Mesh/periodical.cpp

Mesh/periodical.h

Mesh/simple3D.cpp

Mesh/simple3D.h

Mesh/voronoi3D.cpp

Numeric/DivideAndConquer.cpp

contrib/lbfgs/CMakeLists.txt

contrib/lbfgs/alglibinternal.cpp

contrib/lbfgs/alglibinternal.h