during feature protection, most of the connected components, in particular on
the bbox boundary, are already represented and ready to start/hint Delaunay
refinement
if the chosen seed lies in a cell that already belongs (wrt Is_in_domain(cc))
to the right connected component, random shooting is canceled and
the loop continues to next seed
there are more than 90% filter failures in calls to
Compare_distance_3()(Point_3, Segment_3, Point_3)
this commits divides by 10 the initialization (protecting ball
placement) time, at least on polyhedral surfaces input
cherry-picked from 72e2c7b27b
Currently we get a number of warnings when building the documentation for Mesh_3:
```
/home/cgal-testsuite/cgal_doc_build/CGAL-5.3.1-I-169/doc/Mesh_3/Mesh_3.txt:743: warning: unable to resolve reference to 'CGAL/Mesh_3/initialize_triangulation_from_labeled_image.h\' for \ref command
/home/cgal-testsuite/cgal_doc_build/CGAL-5.3.1-I-169/doc/Mesh_3/Mesh_3.txt:801: warning: unable to resolve reference to 'Mesh_3/random_labeled_image.h\' for \ref command
/home/cgal-testsuite/cgal_doc_build/CGAL-5.3.1-I-169/doc/Mesh_3/Mesh_3.txt:817: warning: unable to resolve reference to 'CGAL/Mesh_3/initialize_triangulation_from_gray_image.h\' for \ref command
```
Note the backslash at the end of the file name.
Most likely an attempt was made to escape the dot to not have it as part of the filename, though at least in doxygen 1.8.13 a closing dot was not seen as part of the filename.
Looking at the other escape character of doxygen: the commercial at sign, this was apparently working as escape in the filename as well, though in doxygen 1.8.15 this was not the case anymore either.
During one of the last changes also the backslash lost this possibility for this case and this is now consistent.
The current change (removing the backslashes) doesn't look like to alter the behavior for the 1.8.13 and master version in respect to CGAL.