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, 1 insertions, 2 deletions

diff --git a/pretyping/patternops.ml b/pretyping/patternops.ml
index d6305d81a8..3344faef8a 100644
--- a/pretyping/patternops.ml
+++ b/pretyping/patternops.ml
@@ -348,8 +348,7 @@ let rec pat_of_raw metas vars = function
   | GHole _ ->
       PMeta None
   | GCast (_,c,_) ->
-      Feedback.msg_warning (strbrk "Cast not taken into account in constr pattern");
-      pat_of_raw metas vars c
+      Errors.error ("Cast not supported in constr pattern")
   | GIf (_,c,(_,None),b1,b2) ->
       PIf (pat_of_raw metas vars c,
            pat_of_raw metas vars b1,pat_of_raw metas vars b2)