sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

Overhaul CAM SG driver IOCTL interfaces.

Make it really work for native FreeBSD programs. Before this it was broken
for years due to different number of pointer dereferences in Linux and
FreeBSD IOCTL paths, permanently returning errors to FreeBSD programs.
This change breaks the driver FreeBSD IOCTL ABI, making it more strict,
but since it was not working any way -- who bother.

Add shims for 32-bit programs on 64-bit host, translating the argument
of the SG_IO IOCTL for both FreeBSD and Linux ABIs.

With this change I was able to run 32-bit Linux sg3_utils tools and simple
32 and 64-bit FreeBSD test tools on both 32 and 64-bit FreeBSD systems.

MFC after: 1 month

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.

A fix for the SG_GET_TIMEOUT function slipped into a previous commit by
accident. Remove the text describing the problem as it is no longer
relevant. Also give real implementations for the GET and SET ioctls.

Add the CAM 'SG' peripheral device. This device implements a subset of the
Linux SCSI SG passthrough device API. The intention is to allow for both
running of Linux apps that want to talk to /dev/sg* nodes, and to facilitate
porting of apps from Linux to FreeBSD. As such, both native and linuxolator
entry points and definitions are provided.

Caveats:
- This does not support the procfs and sysfs nodes that the Linux SG
driver provides. Some Linux apps may rely on these for operation,
others may only use them for informational purposes.
- More ioctls need to be implemented.
- Linux uses a naming scheme of "sg[a-z]" for devices, while FreeBSD uses a
scheme of "sg[0-9]". Devfs aliasis (symlinks) are automatically created
to link the two together. However, tools like camcontrol only see the
native names.
- Some operations were originally designed to return byte counts or other
data directly as the syscall return value. The linuxolator doesn't appear
to support this well, so this driver just punts for these cases.

Now that the driver is in place, others are welcome to add missing
functionality. Thanks to Roman Divacky for pushing this work along.