Typo dans message d'erreur (obligations).

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16336 85f007b7-540e-0410-9357-904b9bb8a0f7
Fixing an old pecularity of "red": head betaiota redexes are now
reduced in order to find some head constant to reduce.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16337 85f007b7-540e-0410-9357-904b9bb8a0f7
Using hnf instead of "intro H" for forcing reduction to a product.
Added full betaiota in hnf. This seems more natural, even if it
changes the strict meaning of hnf. This is source of incompatibilities
as "intro" might succeed more often.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16338 85f007b7-540e-0410-9357-904b9bb8a0f7