colors: Fix issue with <lisp> tags too early in #title

colors: Fix issue with <lisp> tags too early in #title

* lisp/muse-colors.el: Split the muse-directive-or-comment property into
  two separate properties that are muse-directive and muse-comment.
  (muse-colors-region-end): Make buffer-local.
  (muse-colors-delayed-commands): New variable that contains a list of
  commands to run immediately after highlighting.  This is meant to allow
  highlighting functions to delay code until later.
  (muse-colors-region): Apply commands in muse-colors-delayed-commands.
  (muse-colors-inhibit-tags-in-directives): New variable that determines
  whether tags are allowed in directives.
  (muse-colors-custom-tags): Take muse-colors-inhibit-tags-in-directives
  into account.
  (muse-unhighlight-region): Remove muse-directive and muse-comment
  properties.
  (muse-colors-title): Modify muse-colors-delayed-commands.
  (muse-colors-title-lisp): New command that gets called after
  highlighting other things.  This interprets <lisp> tags, and is passed
  arguments specifying the beginning and end of the region.  Thanks to
  Junichi Uekawa for the report.  The reason we want to do things this
  way is because this is the behavior we get already when publishing the
  page.

* lisp/muse.el (muse-goto-tag-end): Change to use muse-comment property
  rather than muse-directive-or-comment.