Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Spelling fixes.

Various fixes like spelling, style and syntax.

Submitted by: ru (thanks!)

The EFI vendor UUID for FreeBSD variables is called EFI_FREEBSD_VARIABLE
and not EFI_FREEBSD_VENDOR (cf. EFI_GLOBAL_VARIABLE).

Introduce libefi -- a library around EFI runtime services and protocols.
This first commit brings 3 functions for enumerating, retrieving,
adding, removing and modifying EFI variables. The immediate use of these
include the insertion of a new boot option as part of the installation
process.

This library uses ioctl(2) requests implemented by io(4) to pass the
requests down through the kernel to EFI. These ioctl requests are only
implemented on ia64, so libefi is currently only enabled on ia64. The
interface is generic and io(4) on mad64/i386 can easily be taught to
handle these once EFI support has been added to the kernel there.