Another try at close_proof that should behave better w.r.t. exception handling.
Tactics defined through TACTIC EXTEND that are only defined as a string do
not create grammar and printing rules anymore, they define Ltac entries
in the module that declares them instead.
Slightly better printer for native ML tactics, in order to disambiguate
them.
Moving argument-free tactics out of the AST into a dedicated
"coretactics.ml4" file.
Fix unification of non-unfoldable primitive projections in evarconv.
Decent error message when a constant is not found
Declare: fix Future management
More fixes of unification with primitive projections (missed cases during the merge).
Obligations are not necessarily opaque.