HEADSUP: DTrace support in current

This is an early headsup for DTrace support being committed
to current. I plan to start committing stuff bit-by-bit
starting a week from now, subject to review of the bits.

As part of this work I will be moving the CDDL sources that
ZFS uses into a separate CDDL-specific tree according to
core_at_ instructions (resulting from their license review).

There will also be minor changes to ZFS to build some
things in an 'opensolaris' kernel module which are shared
with DTrace. Both the zfs and dtrace kernel modules will
depend on the opensolaris module.

I am not planning to commit all of DTrace in one big blob.
Instead I want to get the changes in without enabling
them in the build right away. The DTrace support is
optional, so I'll try not to break the build. (famous last
words?)

--
John Birrell