Fixing the "capture" check newly introduced in r15122 when internalizing declaration of contexts of the form "(x y : P x)": - don't forget to catch the error in intern_context; - check capture on glob_constr rather than constr_expr so that binders   possibly introduced by notations are recognized as such; - give a more expressive error message.
Fixing the "capture" check newly introduced in r15122 when
internalizing declaration of contexts of the form "(x y : P x)":
- don't forget to catch the error in intern_context;
- check capture on glob_constr rather than constr_expr so that binders
  possibly introduced by notations are recognized as such;
- give a more expressive error message.

git-svn-id: 44dc50bdcc0f5d1a212c497508dc9452e0b35e2b@15123 85f007b7-540e-0410-9357-904b9bb8a0f7

maximedenes/native-coq,maximedenes/native-coq,maximedenes/native-coq