squid: bump to version 3.5.6

- Bump to version 3.5.6
- Update hash file
- Change configure options according to release notes

Release notes:

  http://www.squid-cache.org/Versions/v3/3.5/squid-3.5.6-RELEASENOTES.html



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>