security/snuffleupagus: update to 0.5.1, build fix

From ChangeLog: https://github.com/jvoisin/snuffleupagus/releases/tag/v0.5.1

• Add support for syslog
• Improve OSX support
• Improve marginally of php8+ compatibility
• Improve php7.4 compatibility
• Improve the default ruleset
• Improve the documentation
• Improve the gitlab CI

Includes build fix for -fno-common issue.

Pet linters.

PR: 248974
Submitted by: franco@opnsense.org (maintainer)
MFH: 2020Q3 (build fix, -fno-common)