Printmod: fresh fake namespaces for non-visible modules (fix #2668, #2983)

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/branches/v8.4@16330 85f007b7-540e-0410-9357-904b9bb8a0f7
Printmod: handle more examples thanks to better nametab use

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/branches/v8.4@16331 85f007b7-540e-0410-9357-904b9bb8a0f7