mac: add macros for 5-argument SDT probes

[kevans]

Summary

A last-minute change to the jail MAC entry points in D53954 is going to
pass the jail_[gs]et(2) flags to mac_prison_check_[gs]et() so that a
policy can, e.g., reject or allow a change if the intent is to
immediately attach, or disallow some fetching of dying jails.