Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Major rework of the ia64 loaders. The two primary objectives are:
1. Make libefi portable by removing ia64 specific code and build
it on i386 and amd64 by default to prevent regressions. These
changes include fixes and improvements over previous code to
establish or improve APIs where none existed or when the amount
of kluging was unacceptably high.
2. Increase the amount of sharing between the efi and ski loaders
to improve maintainability of the loaders and simplify making
changes to the loader-kernel handshaking in the future.

The version of the efi and ski loaders are now both changed to 1.2
as user visible improvements and changes have been made.

Forced commit to document that the following repo copy has been
performed:

from: src/sys/boot/efi/libefi/bootinfo.c
to: src/sys/boot/ia64/common/bootinfo.c

from: src/sys/boot/efi/libefi/copy.c
to: src/sys/boot/ia64/common/copy.c

from: src/sys/boot/efi/libefi/devicename.c
to: src/sys/boot/ia64/common/devicename.c

from: src/sys/boot/efi/libefi/elf_freebsd.c
to: src/sys/boot/ia64/common/exec.c

ncvs meister: simon (thanks!)

Extend struct devdesc with a unit field, called d_unit. Promote the
device (kind) specific unit field to the common field. This change
allows a future version of libefi to work without requiring anything
more than what is defined in struct devdesc and as such makes it
possible to compile said version of libefi for different platforms
without requiring that those platforms have identical derivatives
of struct devdesc.

Convert to __FBSDID.

Reformat.

First approximation of an ia64 EFI loader. Not functional.