squid: Update to 4.4 (stable)

squid: Update to 4.4 (stable)

For details see:
http://www.squid-cache.org/Versions/v4/changesets/

In July 2018, 'squid 4' was "released for production use", see:
https://wiki.squid-cache.org/Squid-4

"The features have been set and large code changes are reserved for later versions."

I've tested almost all 4.x-versions and patch series before with good results.
Right now, 4.4 is running here with no seen problems together with
'squidclamav', 'squidguard' and 'privoxy'.

I too would declare this version stable.

Best,
Matthias

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>