Remove the Sigma (monotonous state) API.

Reminder of (some of) the reasons for removal:

- Despite the claim in sigma.mli, it does *not* prevent evar
  leaks, something like:

  fun env evd ->
  let (evd',ev) = new_evar env evd in
  (evd,ev)

  will typecheck even with Sigma-like type annotations (with a proof of
  reflexivity)

- The API stayed embryonic. Even typing functions were not ported to
  Sigma.

- Some unsafe combinators (Unsafe.tclEVARS) were replaced with slightly
  less unsafe ones (e.g. s_enter), but those ones were not marked unsafe
  at all (despite still being so).

- There was no good story for higher order functions manipulating evar
  maps. Without higher order, one can most of the time get away with
  reusing the same name for the updated evar map.

- Most of the code doing complex things with evar maps was using unsafe
  casts to sigma. This code should be fixed, but this is an orthogonal
  issue.

Of course, this was showing a nice and elegant use of GADTs, but the
cost/benefit ratio in practice did not seem good.

1 files changed, 4 insertions, 5 deletions

diff --git a/plugins/firstorder/ground.ml b/plugins/firstorder/ground.ml
index ab1dd07c11..0fa3089e73 100644
--- a/plugins/firstorder/ground.ml
+++ b/plugins/firstorder/ground.ml
@@ -14,7 +14,6 @@ open Instances
 open Term
 open Tacmach.New
 open Tacticals.New
-open Proofview.Notations
 
 let update_flags ()=
   let predref=ref Names.Cpred.empty in
@@ -31,10 +30,10 @@ let update_flags ()=
       (Names.Id.Pred.full,Names.Cpred.complement !predref)
 
 let ground_tac solver startseq =
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
   update_flags ();
   let rec toptac skipped seq =
-    Proofview.Goal.enter { enter = begin fun gl ->
+    Proofview.Goal.enter begin fun gl ->
     let () =
       if Tacinterp.get_debug()=Tactic_debug.DebugOn 0
       then
@@ -127,7 +126,7 @@ let ground_tac solver startseq =
 		  end
 	    with Heap.EmptyHeap->solver
       end
-    end } in
+    end in
     let n = List.length (Proofview.Goal.hyps gl) in
     startseq (fun seq -> wrap n true (toptac []) seq)
-  end }
+  end