package/squid: security bump to version 4.13

Fixes the following security issues:

CVE-2020-15810: HTTP(S) Request Smuggling
Due to incorrect data validation Squid is vulnerable to HTTP Request
Smuggling attacks against HTTP and HTTPS traffic.  This leads to cache
poisoning.
https://github.com/squid-cache/squid/security/advisories/GHSA-3365-q9qx-f98m

CVE-2020-15811: HTTP(S) Request Splitting
Due to incorrect data validation Squid is vulnerable to HTTP Request
Splitting attacks against HTTP and HTTPS traffic.  This leads to cache
poisoning.
https://github.com/squid-cache/squid/security/advisories/GHSA-c7p8-xqhm-49wv

CVE-2020-24606: Denial of Service processing Cache Digest Response
Due to Improper Input Validation Squid is vulnerable to a Denial of Service
attack against the machine operating Squid.
https://github.com/squid-cache/squid/security/advisories/GHSA-vvj7-xjgq-g2jg



Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>