Fixing bug #2978 (coqide printing debug messages when not in debug mode).

Typical situations concerned by this were when finding word displayed
under pointer for Fn functions.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/branches/v8.4@16190 85f007b7-540e-0410-9357-904b9bb8a0f7