Fix bug that blocked ZFS_IMMUTABLE from being unset.

OS X seems to include AT_MODE in the mask provided to zfs_settattr
even when zp->z_pflags & ZFS_IMMUTABLE is true. So we must not
return EPERM just because the mask includes AT_MODE.

Without this change, running chflags uchg on a file would cause the
file to be undeletable, even by root. ls -lO would not show the
uchg flag as being there, and chflags nouchg would be denied.
Nonetheless, the file could still be deleted after an export and
import.
Attempt to protect against vnop_readdir bcopy panic
Merge branch 'master' of github.com:zfs-osx/zfs
ZVOL: fix the leaks of holds, fix the auto unmount of volumes
zpool_vdev_name now returns disk# instead of disk#s# for whole-disk vdevs.

We were using Linux's strip_partition function, which is specific to
Linux's naming conventions for devices. Now, to determine the name of
a whole-disk vdev, we strip off s# from the BSD name disk#s#.

Misreporting the vdev name was causing the following issue, and perhaps
other similar issues.

The command

    zpool attach -f tank disk2s1 disk3

would fail if the the user originally created the pool with the command

     zpool create -f tank disk2

even though zpool status was reporting the vdev to be disk2s1 not disk2.

With this fix, zpool status will now report disk2, so that the user knows
the attach command should be

    zpool attach -f tank disk2 disk3

in the case of a whole-disk vdev.

It will continue to be the case that if the create command had been

    zpool create tank disk2s1

then zpool status will report the vdev to be disk2s1, and the user is
expected to use disk2s1 in the attach command.
Memory leaks and variable initialisation fixes, from instrumenting tools.
vnop_readdir for !extended was returning bad data.
Configurable install directory for zfs.kext

Naming the configure option --with-kernel-modprefix to be consistent
with the same option's name in the spl.
Fixed regression caused by VATTR_SET_SUPPORTED(vap, va_acl)

Users were experiencing hangs on import. Need to find out what
xnu is expecting before we put this back in.
Fix for the -g annoyances during build.
Move -g0 to the $(COMPILE) line to please Mavericks.
Initial onexit handler for OSX, relying on current_proc().

Attempt to change zfs recv to use unix domain socket instead of mkfifo
Use new SPL getf/releasef and roll back to normal ZFS source code
Remove unknown macros
Update zfs recv to use new SPL
Unfix ZOL function name back to ZFS
Use the proper macro for VN_RDWR
Rollback
Remove userland pipe juggle
Remove debug code, change onexit_fd_hold to call getf/releasef from SPL