IPv6 support and additional PNA bypasses

[gdncc]

Added Basic Experimental Support for IPv6.

This changes the DNS name and URLs format from e.g.:

• "s-ip.ad.dr.ss-127.0.0.1-<random_number>-fs-e.dynamic.your.domain"

to:

• "s-X.Y-<random_number>-fs-e.dynamic.your.domain"

where X and Y are either 4 bytes (IPv4), or 16 bytes (IPv6) hexstrings, or CNAMEs e.g. "localhost".

Sample (re-)tested configurations in Firefox:

• IPv4 public to 127.0.01 (First then Second, fetch API)
• IPv4 public to 127.0.01 (Multiple Answers, fetch API)
• IPv4 public to "localhost" CNAME (First then Second, fetch API)
• IPv6 public to :: (First then Second, fetch API)
• IPv6 public to :: (Multiple Answers, fetch API)

Sample tested PNA bypasses working in Chrome:

• IPv6 public to 127.0.0.1 in ~3 seconds (Multiple Answers, inline frame)
• IPv6 public to :: in ~3 seconds (Multiple Answers, inline frame)
• IPv6 public to 0.0.0.0 in ~3 seconds (Multiple Answers, inline frame)

Added -ignoreDNSRequestFrom Command Line Option

Permits to ignore spurious DNS requests from third-parties that interfere with Singularity's DNS rebinding sessions with targets.