URN support

URNs are location independent persistent resource names, defined as: 
 urn:namespace identifier:namespace specific string
If URN suffix is URL suffix, it's trivial to support URNs too:

  urn:mirror:gnome/gnome-1.0

This would be equivalent to 

  ftp://ftp.gnome.org/pub/GNOME/gnome-1.0
  ftp://ftp.net.lut.ac.uk/gnome/gnome-1.0
In Squid 
  urn:urn_resolver_name:url
Then 
  urn:tracker.foo.net:ftp://ftp.gnome.org/pub/GNOME/gnome-1.0
will lead to the following HTTP request to the tracker.foo.net: 
GET /uri-res/N2L?ftp://ftp.gnome.org/pub/GNOME/gnome-1.0 HTTP/1.0
Copyright © 2000, Martin Hamilton and Alexei Novikov. All rights reserved. This is free slideware, you can redistribute it under the terms of the GNU General Public License, version 2 or later.