Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Move mac.conf to lib/libc/posix1e/

This leverages CONFS to handle the install of the config file.

Approved by: re (blanket, pkgbase), will (mentor)
Differential Revision: https://reviews.freebsd.org/D17162