MFC r277300 (by smh): Mechanically convert cddl sun #ifdef's to illumos

Since the upstream for cddl code is now illumos not sun, mechanically
convert all sun #ifdef's to illumos #ifdef's which have been used in all
newer code for some time.

Also do a manual pass to correct the use if #ifdef comments as per style(9)
as well as few uses of #if defined(__FreeBSD__) vs #ifndef illumos.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Fix -Wmissing-variable-declarations compiler warnings.

References:
https://www.illumos.org/issues/3700

We need to be consistent with prototype definitions. It isn't OK to
use 'const' and just override it whenever we feel like it. If we use
it at all, then we need to do it properly.

Add a couple of functions that were useful in getting this code ported.

This commit was generated by cvs2svn to compensate for changes in r178528,
which included commits to RCS files with non-trunk default branches.

Vendor import of the full userland contrib part of DTrace support from
OpenSolaris. This commit resets files to match the versions in the
OpenSolaris tree as of 2008/04/10.

The changes in this import from the previous import are the ones that
will subsequently re-applied to take files off the vendor branch. This
is unfortunately necessary because the Solaris developers won't allow
FreeBSD support #ifdefs in their source code because that creates
'dead code' (stuff that they never compile).

Vendor import of the CTF (Compact C Type Format) code used by DTrace
from OpenSolaris.