A new infrastructure for warnings.

On the user side, coqtop and coqc take a list of warning names or categories
after -w. No prefix means activate the warning, a "-" prefix means deactivate
it, and "+" means turn the warning into an error. Special categories include
"all", and "default" which contains the warnings enabled by default.

We also provide a vernacular Set Warnings which takes the same flags as argument.

Note that coqc now prints warnings.

The name and category of a warning are printed with the warning itself.

On the developer side, Feedback.msg_warning is still accessible, but the
recommended way to print a warning is in two steps:

1) create it by:

let warn_my_warning =
  CWarnings.create ~name:"my-warning" ~category:"my-category"
    (fun args -> Pp.strbrk ...)

2) print it by:

warn_my_warning args

1 files changed, 2 insertions, 0 deletions

diff --git a/pretyping/glob_ops.mli b/pretyping/glob_ops.mli
index e0a2de032..c2b27ca6a 100644
--- a/pretyping/glob_ops.mli
+++ b/pretyping/glob_ops.mli
@@ -34,6 +34,8 @@ val map_glob_constr :
 val map_glob_constr_left_to_right :
   (glob_constr -> glob_constr) -> glob_constr -> glob_constr
 
+val warn_variable_collision : ?loc:Loc.t -> Id.t -> unit
+
 val fold_glob_constr : ('a -> glob_constr -> 'a) -> 'a -> glob_constr -> 'a
 val iter_glob_constr : (glob_constr -> unit) -> glob_constr -> unit
 val occur_glob_constr : Id.t -> glob_constr -> bool