v8.4: Fixed bug #2955 (anomaly when calling simpl on constants from aliased modules).

The cache for simpl was not consistently behaving wrt modules: entries
were compared with canonical name only but how far to unfold was
relying on full kernel name. Adopted indexation on full kernel names
(though the other choice is probably ok too).

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/branches/v8.4@16178 85f007b7-540e-0410-9357-904b9bb8a0f7