v8.4: Slightly improving some debugging printing and error message for modules.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/branches/v8.4@16154 85f007b7-540e-0410-9357-904b9bb8a0f7
v8.4: Fixed bug #2967 (missing check on ill-formed recursive notation strings).

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/branches/v8.4@16156 85f007b7-540e-0410-9357-904b9bb8a0f7