perror(1): Capsicumise

Signed-off-by: Faraz Vahedi <kfv@kfv.io>
Reviewed by: markj, oshogbo
MFC after: 1 week
Pull Request: https://github.com/freebsd/freebsd-src/pull/1492

(cherry picked from commit adc02d5e3cfad9c9d7e12f776cad651795d9ad78)