CC Mode: Add/remove defun buffer locally to post-command-hook

CC Mode: Add/remove defun buffer locally to post-command-hook

Also remove no longer existing hook.

* lisp/progmodes/cc-mode (c-leave-cc-mode-mode): remove-hook
c-post-command buffer locally.  Delete removal of non-existent
c-post-gc-hook.
(c-basic-common-init): add-hook c-post-command buffer locally.

(cherry picked from commit c05a13ef0dc69497e275b627dbc8e2b25ece7711)