gpt - Add a new directive called 'init'
* Add a new directive called 'init'. This directive works like
gpt create except it will also create a msdos slice 0 (and newfs_msdos
it), and a "DragonFly Label64" slice 1, and
'disklabel -r -w <slice1> auto'.
* If -B is also specified, the init directive will populate the msdos
filesystem with efi/boot/bootx64.efi, and also supplies -B to the
disklabel command.
* This command does not create the boot, swap, or root filesystem
partitions in the disklabel. It is meant to do something similar
to what fdisk -IB used to do for us for legacy partitions (though
I should note that fdisk -IB didn't initialize a new disklabel). But
we do for gpt.
UnifiedSplitRaw
