OK, a first reasonable attempt at a solaris module/chdev shim layer.

OK, a first reasonable attempt at a solaris module/chdev shim layer.
This should handle the absolute minimum I need for ZFS.  It will
register the chdev with the right callbacks.  Then the generic
registered linux callback will find the right registered solaris
callback for the function and munge the args just right before
passing it on.  Should work, but untested (just compiled), so I
expect bugs.

git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@52 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c