[PATCH] OpenSolaris/ZFS: C++ compatibility

The attached patch is sufficient to allow a C++ program to use libzfs.
The motivation for these changes is work I'm doing on a ZFS fault
handling daemon that is written in C++.  SpectraLogic's intention
is to return this work to the FreeBSD project once it is a bit more
complete.

Since these changes modify files that come from OpenSolaris, I want to be
sure I understand the project's policies regarding divergence from
the vendor before I check them in.  All of the changes save one should
be trivial to merge with vendor changes and I will do that work for the
v28 import.  Is there any reason I should not commit these changes?

Thanks,
Justin