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.
header = header-rss.tmpl
changelog = changelog-rss.tmpl
changelogentry = changelogentry-rss.tmpl
filelog = filelog-rss.tmpl
filelogentry = filelogentry-rss.tmpl