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

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

Move most of the contents of opt_compat.h to opt_global.h.

opt_compat.h is mentioned in nearly 180 files. In-progress network
driver compabibility improvements may add over 100 more so this is
closer to "just about everywhere" than "only some files" per the
guidance in sys/conf/options.

Keep COMPAT_LINUX32 in opt_compat.h as it is confined to a subset of
sys/compat/linux/*.c. A fake _COMPAT_LINUX option ensure opt_compat.h
is created on all architectures.

Move COMPAT_LINUXKPI to opt_dontuse.h as it is only used to control the
set of compiled files.

Reviewed by: kib, cem, jhb, jtl
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14941

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

Fix 'make depend'

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

Add missing opt_compat.h dependency.

Found by: Garrett Cooper

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

Change filesystem name from mqueue to mqueuefs for style consistent.

Suggested by: rwatson

Compile mqueue module.