[build] Split stdlib to it's own opam package.

We introduce a new package structure for Coq:

- `coq-core`: Coq's OCaml tools code and plugins
- `coq-stdlib`: Coq's stdlib [.vo files]
- `coq`: meta-package that pulls `coq-{core,stdlib}`

This has several advantages, in particular it allows to install Coq
without the stdlib which is useful in several scenarios, it also open
the door towards a versioning of the stdlib at the package level.

The main user-visible change is that Coq's ML development files now
live in `$lib/coq-core`, for compatibility in the regular build we
install a symlink and support both setups for a while.

Note that plugin developers and even `coq_makefile` should actually
rely on `ocamlfind` to locate Coq's OCaml libs as to be more robust.

There is a transient state where we actually look for both
`$coqlib/plugins` and `$coqlib/../coq-core/plugins` as to support
the non-ocamlfind plus custom variables.

This will be much improved once #13617 is merged (which requires this
PR first), then, we will introduce a `coq.boot` library so finally
`coqdep`, `coqchk`, etc... can share the same path setup code.

IMHO the plan should work fine.

1 files changed, 2 insertions, 2 deletions

diff --git a/doc/plugin_tutorial/tuto2/src/dune b/doc/plugin_tutorial/tuto2/src/dune
index 8c4b04b1ae..0797debccf 100644
--- a/doc/plugin_tutorial/tuto2/src/dune
+++ b/doc/plugin_tutorial/tuto2/src/dune
@@ -1,6 +1,6 @@
 (library
  (name tuto2_plugin)
- (public_name coq.plugins.tutorial.p2)
- (libraries coq.plugins.ltac))
+ (public_name coq-core.plugins.tutorial.p2)
+ (libraries coq-core.plugins.ltac))
 
 (coq.pp (modules g_tuto2))