When the hostname is an IPv6 literal, encapsulate it

with [brackets] before calling Net::HTTP  [rt.cpan.org #29468]

See also https://github.com/libwww-perl/net-http/pull/10 to complete IPv6 support 
for LWP's HTTP/HTTPS modes.

I wonder if all versions of all socket classes can handle the bracketed hostnames -- should this be limited to IP addresses (check for ".") and potentially a version of Net::HTTP that handles it propery (6.07)?