Remove $FreeBSD$: one-line sh pattern

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

Disable fsck_ffs for now, 4MB target size issues.

Import the first cut of "bsdbox".

This uses the existing crunchgen infrastructure to build
a series of tools designed to replace the base and networking
tools on an embedded system.

It reuses 'bsd.crunchgen.mk' to drive the actual file
creation. The rescue build system also uses this.

Unlike busybox, it doesn't include its own source - instead,
it just builds from the sources in /usr/src/ and leverages
the existing BSD framework.

Thie is still quite messy and could do with a whole lot of
cleaning up. However it is proving to be very useful with
my current build framework, allowing me to build binary root
images that are about 30% less than simply cherrypicking files
and libraries from an installworld.