Add a multi-repository server
This merges a bunch of the ideas for a multi-repository CGI script and
simplifies things a bit.
It uses PATH_INFO so it generally wants paths of the form:
http://host/hg.cgi/virtualpath
This gets mapped via a simple config file to the real path. All info
about the repo is read from the repo's hgrc.
<item>
<title>#desc|firstline|escape#</title>
<link>#url#?cmd=file;file=#file#;filenode=#filenode#</link>
<description><![CDATA[#desc|escape|addbreaks#]]></description>
<author>#author|obfuscate#</author>
<pubDate>#date|rfc822date#</pubDate>>
</item>