unittests to display #761 issue.

libhtp doesn't parse host correctly if uri/host_header contains ipv6 address.
fix for #571.

Backport 8bbcdb61cf8e014294be0caf6d6e614ef778c7b4 changes from libhtp 0.5.x
to Suricata's bundled libhtp.

We now handle ipv6 addresses in uri and host header.