sys: Remove $FreeBSD$: one-line sh pattern

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

sys/modules: normalize .CURDIR-relative paths to SRCTOP

This simplifies make output/logic

Tested with: `cd sys/modules; make ALL_MODULES=` on amd64
MFC after: 1 month
Sponsored by: Dell EMC Isilon

Move most of the 15 variations on generating opt_inet.h and
opt_inet6.h into kmod.mk by forcing almost everybody to eat the same
dogfood. While at it, consolidate the opt_bpf.h and opt_mroute.h
targets here too.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

- Import the HEAD csup code which is the basis for the cvsmode work.

Per email to arch@ a little while ago (that was greeted with silence),
prefer the more common > ${.TARGET} over > opt_foo.h in modules
makefiles.

Multi-bss (aka vap) support for 802.11 devices.

Note this includes changes to all drivers and moves some device firmware
loading to use firmware(9) and a separate module (e.g. ral). Also there
no longer are separate wlan_scan* modules; this functionality is now
bundled into the wlan module.

Supported by: Hobnob and Marvell
Reviewed by: many
Obtained from: Atheros (some bits)