Wextra results in a dreadful wall of yellow in the test-suite and is
scary when using CGAL. Reduce some of the noise by silencing the
obvious cases with CGAL_USE or comments.
* Minor fix in Polyhedral_mesh_domain_3: internal AABB kd-tree is now built
* Minor fix in mesh_standard_facet_criteria.h: check dimension with >2 instead of ==2 & add some assertions
* Add internal(undocumented) usefull genericity:
+ add Wrapper template parameter (with default value) in Implicit_mesh_domain_3
+ add Wrapper template parameter (with default value) in Labeled_Image_mesh_domain_3
+ add two template parameters (with defaults) in Mesh_criteria_3