Attached patch affects how 'info' links in org mode are converted to HTML

links.  Today info links such as

    [[info:emacs#List Buffers]]

are converted to this HTML link:

    <a href="emacs.html#List-Buffers">emacs#List Buffers</a>

With the patch applied, the HTML link generated would be

    <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#List-Buffers">emacs#List Buffers</a>

The general idea is that couple of list variables describe how to map

info file names to URLs so that those URL's would be used if available.

One motivation for this patch is to make it easy for elisp package

authors to to create links to wonderful emacs documents, because writing

an org info-link to emacs manual in org files is trivial once you know

the info node name.