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

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

make 'make universe' not complain about
In file included from /src/sys/modules/powermac_nvram/../../dev/powermac_nvram/powermac_nvram.c:38:
@/dev/ofw/ofw_bus.h:36:24: error: ofw_bus_if.h: No such file or directory
I am not sure for how long this had not worked and if it was just the
latest vimage commit that had revealed this or if nobody had built
universe successfully in a while. Btw, the tinderbox did not complain
either so that is probably the reason noone had noticed.

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

Add missing headers.

Add device to access and modify Open Firmware NVRAM settings in
PowerPC-based Apple's machines and small utility to do it from
userland modelled after the similar utility in Darwin/OSX.

Only tested on 1.25GHz G4 Mac Mini.

MFC after: 1 month