[numeral] [plugins] Switch from `Big_int` to ZArith.

We replace Coq's use of `Big_int` and `num` by the ZArith OCaml
library which is a more modern version.

We switch the core files and easy plugins only for now, more complex
numerical plugins will be done in their own commit.

We thus keep the num library linked for now until all plugins are
ported.

Co-authored-by: Vincent Laporte <Vincent.Laporte@fondation-inria.fr>

1 files changed, 1 insertions, 0 deletions

diff --git a/coq.opam b/coq.opam
index 23cef68dce..f44223052d 100644
--- a/coq.opam
+++ b/coq.opam
@@ -25,6 +25,7 @@ depends: [
   "dune"      { >= "2.5.0"  }
   "ocamlfind" { build }
   "num"
+  "zarith"    { >= "1.9.1" }
 ]
 
 build: [