Documenting the previous commit: Existing Instance with priority.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16646 85f007b7-540e-0410-9357-904b9bb8a0f7
Added printing of instance priority to the Print Instances command.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16647 85f007b7-540e-0410-9357-904b9bb8a0f7