Make sure spaces in HTML URLs get escaped properly.

Make sure spaces in HTML URLs get escaped properly.

* lisp/muse-docbook.el (muse-docbook-markup-specials): Move to
  muse-xml-common.el.

* lisp/muse-html.el (muse-html-markup-specials): Ditto.

* lisp/muse-xml.el (muse-xml-markup-specials): Ditto.

* lisp/muse-html.el (muse-html-prepare-buffer): Don't modify
  muse-publish-url-transforms.

* lisp/muse-publish.el (muse-publish-escape-specials): Get specials only
  once, rather than once-per-iteration.
  (muse-publish-escape-specials-in-string): If a function is returned by
  a function in :specials, pass it the string and use the results.  This
  allows us to deal with funky cases like HTML URLs which work on a
  negated subset, by passing the buck.  We don't permit this behavior in
  muse-publish-escape-specials because there hasn't been a need, yet.

* lisp/muse-xml-common.el (muse-xml-markup-specials): New option that
  specifies the specials to normally escape.
  (muse-xml-markup-specials-url-extra): New option that specifies the
  extra specials to escape in URLs.  Thanks to John Sullivan for
  reporting the incorrect translation of the space character in URLs.
  (muse-xml-decide-specials): New function that determines the specials
  to escape, given context.
  (muse-xml-escape-url): Rename from muse-xml-escape-string.  Add "%" to
  the list of characters to ignore.  Fix code indentation.
git-archimport-id: mwolson@gnu.org--2005/muse--main--1.0--patch-321