Remove $FreeBSD$: one-line sh pattern

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

META MODE: These need object directories to handle staging.

Sponsored by: EMC / Isilon Storage Division

Follow-up to r255036; remove beforeinstall directives from bsdconfig(8)
Makefile's, fixing concurrent installworld (`make -j17 installworld').

Thanks to: delphij, emaste
Reviewed by: delphij
MFC after: 3 days
X-MFC-to: stable/10, stable/9

Add new `includes' module for exploring the bsdconfig(8) API.