[PATCH 0 of 1] Recursively look for possible repos in hgweb.config

Currently hgweb.hgwebdir reads the entries defined in hgweb.config
[paths] as being:

virtual/path = real/path

This patch allows real/path to be searched recursively for hg
repositories such that with a dir structure:

/mercurial/
    + developers/
            + develA/   (hg repository)
            + develB/   (hg repository)
            + randomFolder
    + cleanTrees/
            + mainLine/ (hg repository)
            + currentProduction (hg repository)

and hgweb.config:

[paths]
everything = mercurial
production = mercurial/cleanTrees/currentProduction

Returns a list of repositories:

everything/developers/develA
everything/developers/develB
everything/cleanTrees/mainLine
everything/cleanTrees/currentProduction
production