[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.

1 files changed, 12 insertions, 0 deletions

diff --git a/CHANGES b/CHANGES
index 3030e3311..aea7ec2f6 100644
--- a/CHANGES
+++ b/CHANGES
@@ -36,6 +36,18 @@ Tactic language
   called by OCaml-defined tactics.
 - Option "Ltac Debug" now applies also to terms built using Ltac functions.
 
+Coq binaries and process model
+
+- Before 8.9, Coq distributed a single `coqtop` binary and a set of
+  dynamically loadable plugins that used to take over the main loop
+  for tasks such as IDE language server or parallel proof checking.
+
+  These plugins have been turned into full-fledged binaries so each
+  different process has associated a particular binary now, in
+  particular `coqidetop` is the CoqIDE language server, and
+  `coq{proof,tactic,query}worker` are in charge of task-specific and
+  parallel proof checking.
+
 Changes from 8.8.0 to 8.8.1
 ===========================