Add :after-hook facility to define-derived-mode.

This allow a form to be evaluated _after_ a major mode's hooks have been run.
It is needed to solve some problems in CC Mode, including bug #16759 and
bug #23476.

* lisp/emacs-lisp/derived.el (define-derived-mode): introduce the new argument
`:after-hook', and generate the requisite code for it.
(derived-mode-make-docstring): Take account of the possibility of :after-hook.

* lisp/subr.el (delayed-after-hook-forms): New variable.
(run-mode-hooks): As the last thing evaluate the forms in
delayed-after-hook-forms.

* doc/lispref/modes.texi (Derived Modes): Document :after-hook.
(Mode Hooks): Document the new feature in run-mode-hooks.

* etc/NEWS: Note the new feature.

1 files changed, 6 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 92d301ecd6f..22eb2eabc37 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -369,6 +369,12 @@ variable.
 
 ** New var syntax-ppss-table to control the syntax-table used in syntax-ppss.
 
++++
+** `define-derived-mode' can now specify an :after-hook form, which
+gets evaluated after the new mode's hook has run.  This can be used to
+incorporate configuration changes made in the mode hook into the
+mode's setup.
+
 ** Autoload files can be generated without timestamps,
 by setting 'autoload-timestamps' to nil.
 FIXME As an experiment, nil is the current default.