Fixed IPv6-related SIP parsing bugs.

(closes issue #17663)
Reported by: oej
Patches:
      diff uploaded by sperreault (license 252)
      diff2 uploaded by sperreault (license 252)
      get_domain.diff uploaded by sperreault (license 252)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@280707 65c4cc65-6c06-0410-ace0-fbb531ad65f3