hxt 3D mesher properly connected

Mesh/meshGRegionHxt.cpp

contrib/hxt/CMakeLists.txt

contrib/hxt/hxt_bbox.c

contrib/hxt/hxt_bbox.h

contrib/hxt/hxt_boundary_recovery.cxx

contrib/hxt/hxt_linear_system_lu.c

contrib/hxt/hxt_linear_system_petsc.c

contrib/hxt/hxt_mesh.c

contrib/hxt/hxt_mesh.h

contrib/hxt/hxt_mesh3d.c

contrib/hxt/hxt_mesh3d.h

contrib/hxt/hxt_mesh3d_main.c

contrib/hxt/hxt_mesh3d_main.h

contrib/hxt/hxt_omp.h

contrib/hxt/hxt_opt.c

contrib/hxt/hxt_opt.h

contrib/hxt/hxt_option.c

contrib/hxt/hxt_option.h

contrib/hxt/hxt_sort.c

contrib/hxt/hxt_sort.h