Support IPv6 URLs

[trinitronx]

Currently, it looks like the IPv6 bracketed IP syntax is not supported.

For example, testing IPv6 access to an HTTP server on port 8000 of IPv6 (example) address 2001:0db8:abcd:ef:a0a:a0a:a0a:3

$ dstp 'http://[2001:0db8:abcd:ef:a0a:a0a:a0a:3]:8000/'
Ping: 33.855667ms
DNS: resolving 2001:0db8:abcd:ef:a0a:a0a:a0a:3
SystemDNS: resolving 2001:0db8:abcd:ef:a0a:a0a:a0a:3
TLS: dial tcp: address 2001:0db8:abcd:ef:a0a:a0a:a0a:3:443: too many colons in address
HTTPS: Get "https://2001:0db8:abcd:ef:a0a:a0a:a0a:3": dial tcp: lookup 2001:0db8:abcd:ef:a0a:a0a:a0a:3: no such host

It looks like the required square brackets [] surrounding the IPv6 address are eaten during parsing, then it tries to directly access 2001:0db8:abcd:ef:a0a:a0a:a0a:3:443 as if it's a hostname on HTTPS port 443 rather than port 8000 as intended. The error returned makes sense, as a hostname should not have that many colons, but an IPv6 address should as long as it's surrounded by square brackets: [2001:0db8:abcd:ef:a0a:a0a:a0a:3]