muse-latex: Add a few escaping options that may be used in the future.
* lisp/muse-latex.el: Note that we don't make use of these new options
yet.
(muse-latex-markup-specials): Move longer escapes out of here.
(muse-latex-markup-specials-entire-document): New option that specifies
the special characters to escape in the whole document after processing
markup rules.
(muse-latex-markup-specials-verbatim): New option that specifies the
special characters to escape in <example> tags and =literal text=.
git-archimport-id: mwolson@gnu.org--2005/muse--main--1.0--patch-241