Fix STUN crash when using IPv6 any address

Ensure that when chan_sip binds to the IPv6 any address ([::]), IPv4
candidates are also added.

(closes issue ASTERISK-21917)
Reported by: Torrey Searle
Patches:
    0023_ipv6_stun_crash.patch uploaded by Torrey Searle (License 5334)
........

Merged revisions 400681 from http://svn.asterisk.org/svn/asterisk/branches/11
........

Merged revisions 400682 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@400684 65c4cc65-6c06-0410-ace0-fbb531ad65f3