[stm] Make toplevels standalone executables.

We turn coqtop "plugins" into standalone executables, which will be
installed in `COQBIN` and located using the standard `PATH`
mechanism. Using dynamic linking for `coqtop` customization didn't
make a lot of sense, given that only one of such "plugins" could be
loaded at a time. This cleans up some code and solves two problems:

- `coqtop` needing to locate plugins,
- dependency issues as plugins in `stm` depended on files in `toplevel`.

In order to implement this, we do some minor cleanup of the toplevel
API, making it functional, and implement uniform build rules. In
particular:

- `stm` and `toplevel` have become library-only directories,
- a new directory, `topbin`, contains the new executables,
- 4 new binaries have been introduced, for coqide and the stm.
- we provide a common and cleaned up way to locate toplevels.

4 files changed, 17 insertions, 33 deletions

diff --git a/ide/coqidetop.mllib b/ide/ide_common.mllib
index df988d8f1..050c282ef 100644
--- a/ide/coqidetop.mllib
+++ b/ide/ide_common.mllib
@@ -5,4 +5,3 @@ Serialize
 Richpp
 Xmlprotocol
 Document
-Ide_slave
diff --git a/ide/ide_slave.mli b/ide/ide_slave.mli
deleted file mode 100644
index 9db9ecd12..000000000
--- a/ide/ide_slave.mli
+++ /dev/null
@@ -1,12 +0,0 @@
-(************************************************************************)
-(*         *   The Coq Proof Assistant / The Coq Development Team       *)
-(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
-(* <O___,, *       (see CREDITS file for the list of authors)           *)
-(*   \VV/  **************************************************************)
-(*    //   *    This file is distributed under the terms of the         *)
-(*         *     GNU Lesser General Public License Version 2.1          *)
-(*         *     (see LICENSE file for the text of the license)         *)
-(************************************************************************)
-
-(* This empty file avoids a race condition that occurs when compiling a .ml file
-   that does not have a corresponding .mli file *)
diff --git a/ide/ide_slave.ml b/ide/idetop.ml
index 6c7ca4f8e..e40af003b 100644
--- a/ide/ide_slave.ml
+++ b/ide/idetop.ml
@@ -457,7 +457,7 @@ let msg_format = ref (fun () ->
 
 (* The loop ignores the command line arguments as the current model delegates
    its handing to the toplevel container. *)
-let loop _args ~state =
+let loop ~opts:_ ~state =
   let open Vernac.State in
   set_doc state.doc;
   init_signal_handler ();
@@ -506,13 +506,16 @@ let rec parse = function
   | x :: rest -> x :: parse rest
   | [] -> []
 
-let () = Coqtop.toploop_init := (fun coq_args extra_args ->
-        let args = parse extra_args in
-        CoqworkmgrApi.(init High);
-        coq_args, args)
-
-let () = Coqtop.toploop_run := loop
-
 let () = Usage.add_to_usage "coqidetop"
 "  --xml_format=Ppcmds    serialize pretty printing messages using the std_ppcmds format\
 \n  --help-XML-protocol    print documentation of the Coq XML protocol\n"
+
+let islave_init ~opts extra_args =
+  let args = parse extra_args in
+  CoqworkmgrApi.(init High);
+  opts, args
+
+let () =
+  let open Coqtop in
+  let custom = { init = islave_init; run = loop; } in
+  start_coq custom
diff --git a/ide/ideutils.ml b/ide/ideutils.ml
index bdb39e94a..e96b99299 100644
--- a/ide/ideutils.ml
+++ b/ide/ideutils.ml
@@ -289,16 +289,10 @@ let coqtop_path () =
     | Some s -> s
     | None ->
       match cmd_coqtop#get with
-	| Some s -> s
-	| None ->
-	  try
-            let old_prog = Sys.executable_name in
-            let pos = String.length old_prog - 6 in
-            let i = Str.search_backward (Str.regexp_string "coqide") old_prog pos
-            in
-            let new_prog = Bytes.of_string old_prog in
-            Bytes.blit_string "coqtop" 0 new_prog i 6;
-            let new_prog = Bytes.to_string new_prog in
+      | Some s -> s
+      | None ->
+        try
+          let new_prog = System.get_toplevel_path "coqidetop" in
             if Sys.file_exists new_prog then new_prog
 	    else
 	      let in_macos_bundle =
@@ -306,8 +300,8 @@ let coqtop_path () =
 		  (Filename.dirname new_prog)
 		  (Filename.concat "../Resources/bin" (Filename.basename new_prog))
 	      in if Sys.file_exists in_macos_bundle then in_macos_bundle
-		 else "coqtop"
-	  with Not_found -> "coqtop"
+                 else "coqidetop"
+        with Not_found -> "coqidetop"
   in file
 
 (* In win32, when a command-line is to be executed via cmd.exe