zfs.fs bundle initial commit

Issues:
- Autotools does not install the zfs.fs bundle. zfs_bundle_install.sh
hack is there in the meantime.

- Breaks Spotlight on automounted pools. If this cannot be fixed
easily, the fs-bundle approach may need to be dropped entirely,
in favor of some sort of launchd hack. Asking users to choose
between Spotlight and automounting is unacceptable.

- Uses altroot to align pools to /Volumes, which may clash with users'
local, non-default mountpoint property settings. /etc/fstab may be
a (wretched) workaround, because diskarbitration respects fstab entries.
MacZFS 74 just defaults to putting everything in /Volumes, rather than
using altroot.

- Printing the pool's GUID to stdout in response to the probe
executable's being called with the -k option does not seem to
work to make OS X aware of a volume UUID. Volume UUID still does
not show up in diskutil info or System Information.

- No implementation of newfs_zfs, fsck_zfs.
fix bundle installer bug
Do not supply UUID to diskarbitration.

Removing handling of '-k' option to the probe executable.
OS X wants something in the format:

    XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX

Even providing a UUID in that format still confuses
Spotlight, though. At least by refusing to handle
'-k' Spotlight can be enabled on the child file systems.

Perhaps this can be restored if Spotlight issues are
addressed first.
Call zpool_enable_datasets once per pool.

We need to check the return code of zpool_import before proceeding
to zpool_enable_datasets. It seems the return code will be 0 for
the call to zpool_import for the first encountered vdev, and non-zero
for all subsequent vdevs. Skipping zpool_enable_datasets for non-zero
return codes from zpool_import should be sufficient to prevent
zpool_enable_datasets from being called more than once on the same
pool.

If we attempt to enable the datasets despite non-zero zpool_import
return code, not all datsets are enabled after boot.
Make llvm-gcc happy.
rm extra zfs_util.c
Check if pool already imported or unavailable.