Removing the dependency of every level of tactic ATSs on glob_tactic_expr.
Instead of putting the body directly in the AST, we register it in a table.

This time it should work properly. Tactic notation are given kernel names to
ensure the unicity of their contents.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@17079 85f007b7-540e-0410-9357-904b9bb8a0f7