The base of (virtual) URL of this server which will be embedded
in each absolute URL generated by the DeleGate: ex. icon URLs
in HTML pages generated by NNTP/HTTP gateway DeleGate.
When an origin/gateway HTTP-DeleGate received "Host:vhost1" in
a request header, it overrides BASEURL="http://vhost0" parameter
to have "vhost1" be the base URL of the DeleGate.
To override the "Host:" header by BASEURL, prefix "-" to a host name as
MOUNT='/* nntp://newsserver/*" BASEURL="http://wwwserver/news"
// this will be useful when a HTTP server "http://wwwserver" is mapping
// its path "/news" to the root of this HTTP-DeleGate.