Feature-request: normalize hostnames in URL

The urls to be cached are currently used verbatim by apt-cacher-ng. This results in multiple cachetrees when the url differs only in the way the hostname in it is spelled (uppercase/lowercase). E.g. http://ftp1.de.FreeBSD.org/freebsd/ vs http://ftp1.de.freebsd.org/freebsd/

Hostnames are not case sensitive, hence a normalization of the hostname to lowercase in the URL would avoid caching files multiple times.