Referer: fixed server_name regex matching.

Referer: fixed server_name regex matching.

The server_name regexes are normally compiled for case-sensitive matching.
This violates case-insensitive obligations in the referer module.  To fix
this, the host string is converted to lower case before matching.

Previously server_name regex was executed against the whole referer string
after dropping the scheme part.  This could led to an improper matching, e.g.:

    server_name ~^localhost$;
    valid_referers server_names;

    Referer: http://localhost/index.html

It was changed to look only at the hostname part.

The server_name regexes are separated into another array to not clash with
regular regexes.