Reorganizing intropatterns: * and ** are not naming intropatterns.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16620 85f007b7-540e-0410-9357-904b9bb8a0f7
Revising r16550 about providing intro patterns for applying injection:
- Introduction of a specific notation for injection intropatterns: [= pats]
- Use of this specific pattern also to apply discriminate on the fly

Note: The automatic injection of dependent tuples over a same first
component (introduced in r10180) still not integrated to the main
parts of injection and its variant (indeed, it applies only for a root
dependent tuple in sigT).

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16621 85f007b7-540e-0410-9357-904b9bb8a0f7