PJPROJECT 2.5.5 introduced a race condition with the -r5349 IPv6 DNS
patch.

The patches below fix the DNS lookup race condition crash caused by
attempting to send the same message twice for the single DNS lookup.

0006-r5471-svn-backport-Various-fixes-for-DNS-IPv6.patch
0006-r5473-svn-backport-Fix-pending-query.patch

The patch below removes a cached DNS response from the hash table when
another thread is referencing the old entry.  The table still contained
the entry when it was destroyed which can result in inexplicable crashes.

0006-r5475-svn-backport-Remove-DNS-cache-entry.patch

ASTERISK-26344 #close
Reported by: Ian Gilmour

ASTERISK-26387 #close
Reported by: Harley Peters

Change-Id: I17fde80359e66f65a91341ceca58d914d0f61cc4