squid: add upstream post-3.5.27 security patches
Fixes the following security issues:
SQUID-2018:1 Due to incorrect pointer handling Squid is vulnerable to denial
of service attack when processing ESI responses.
http://www.squid-cache.org/Advisories/SQUID-2018_1.txt
SQUID-2018:2 Due to incorrect pointer handling Squid is vulnerable to
denial of service attack when processing ESI responses or downloading
intermediate CA certificates.
http://www.squid-cache.org/Advisories/SQUID-2018_2.txt
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>