Try to fix failure to recognize Muse file extension (6th attempt).

Try to fix failure to recognize Muse file extension (6th attempt).

* lisp/muse-mode.el: Call `muse-mode-maybe-after-init' after the user's
  init file is loaded.
  (muse-mode-maybe-after-init): New function that causes muse-mode-maybe
  to be added to find-file-hooks when muse-mode-auto-p is non-nil.

* lisp/muse.el: Call `muse-update-file-extension-after-init after the
  user's init file is loaded.  Explicitly add the Muse file extension
  when muse.el is loaded, to make life simpler.
  (muse-update-file-extension): Take several edge cases into account.
  (muse-file-extension): Docfix.
  (muse-update-file-extension-after-init): New function that causes the
  file extension to be updated.

* muse.texi (Projects): It is no longer necessary to call
  `muse-mode-maybe' manually.
git-archimport-id: mwolson@gnu.org--2006/muse--main--1.0--patch-105