Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Add ZFS support to the bsdinstall partition editor and sade.

Submitted by: Kurt Lidl (original version)
MFC after: 6 weeks

Add EFI support to the installer. This requires that the kernel provide
a sysctl to determine what firmware is in use. This sysctl does not exist
yet, so the following blocks are in front of the wheels:
- I've provisionally called this "hw.platform" after the equivalent thing
on PPC
- The logic to check the sysctl is short-circuited to always choose BIOS.
There's a comment in the top of the file about how to turn this off.

If IA64 acquired a boot1.efifat-like thing (probably with very few
modifications), the same code could be adapted there.

Import bsdinstall. This is meant to be (eventually in conjunction with
pc-sysinstall) a replacement for sysinstall in the 9.0 release and beyond.
Currently supported platforms are sparc64, pc98, i386, amd64, powerpc, and
powerpc64. Integration into the build system will occur in the coming
weeks.

Merging with pc-sysinstall will use this code as a frontend, while
temporarily retaining the interactive partition editor here. This work
will be done in parallel with improvements on this code and release
integration.

Thanks to all who have provided testing and comments!