Integrate build and documentation of Ltac2

Since Ltac2 cannot be put under the stdlib logical root (some file names
would clash), we move it to the `user-contrib` directory, to avoid adding
another hardcoded path in `coqinit.ml`, following a suggestion by @ejgallego.

Thanks to @Zimmi48 for the thorough documentation review and the
numerous suggestions.

1 files changed, 25 insertions, 0 deletions

diff --git a/user-contrib/Ltac2/Message.v b/user-contrib/Ltac2/Message.v
new file mode 100644
index 0000000000..7bffe0746b
--- /dev/null
+++ b/user-contrib/Ltac2/Message.v
@@ -0,0 +1,25 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+Require Import Ltac2.Init.
+
+Ltac2 @ external print : message -> unit := "ltac2" "print".
+
+Ltac2 @ external of_string : string -> message := "ltac2" "message_of_string".
+
+Ltac2 @ external of_int : int -> message := "ltac2" "message_of_int".
+
+Ltac2 @ external of_ident : ident -> message := "ltac2" "message_of_ident".
+
+Ltac2 @ external of_constr : constr -> message := "ltac2" "message_of_constr".
+(** Panics if there is more than one goal under focus. *)
+
+Ltac2 @ external of_exn : exn -> message := "ltac2" "message_of_exn".
+(** Panics if there is more than one goal under focus. *)
+
+Ltac2 @ external concat : message -> message -> message := "ltac2" "message_concat".