Allow transform function for link descriptions. Bare email and URL fixes.

Allow transform function for link descriptions.  Bare email and URL fixes.

* lisp/muse-publish.el (muse-publish-url-transforms): Docfix.
  (muse-publish-desc-transforms): New option that contains the functions
  that will be called to transform a link description.
  (muse-publish-markup-word): Handle Yet Another Edge Case.
  (muse-publish-markup-email): Use
  `muse-publish-escape-specials-in-string'.  Don't publish if we have a
  double-quote on either side.
  (muse-publish-url): Apply description transforms.
  (muse-publish-markup-url): Don't publish if we have a double-quote on
  either side.

* lisp/muse-wiki.el (muse-wiki-update-wikiword-regexp)
  (muse-wiki-wikiword-regexp, muse-wiki-use-wikiword): Minor docfixes.
  (muse-wiki-interwiki-delimiter): New option that indicates the
  interwiki delimiter to use.
  (muse-wiki-interwiki-replacement): New option that indicates the
  replacement
  (muse-wiki-update-interwiki-regexp): Use muse-wiki-interwiki-delimiter.
  (muse-wiki-publish-pretty-title): Deal with EXPLICIT argument so that
  this can be added to muse-publish-desc-transforms.
  (muse-wiki-publish-pretty-interwiki): New function that replaces the
  interwiki delimiter with its replacement, but only when the given text
  is not an explicit link.

* lisp/muse.el (muse-update-file-extension): New function made from the
  innards of the :set function in `muse-file-extension'.
git-archimport-id: mwolson@gnu.org--2005/muse--main--1.0--patch-185