package/snort: security bump to version 2.9.18.1

Fix CVE-2021-40114: Multiple Cisco products are affected by a
vulnerability in the way the Snort detection engine processes ICMP
traffic that could allow an unauthenticated, remote attacker to cause a
denial of service (DoS) condition on an affected device. The
vulnerability is due to improper memory resource management while the
Snort detection engine is processing ICMP packets. An attacker could
exploit this vulnerability by sending a series of ICMP packets through
an affected device. A successful exploit could allow the attacker to
exhaust resources on the affected device, causing the device to reload.

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-s2R7W9UU
https://www.snort.org/downloads/snort/changelog_2.9.18.1.txt



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>