* have pr_stat return EOPNOTSUPP consistently for all protocols that do
  not fill in struct stat instead of returning success.

* in pr_stat remove all checks for non-NULL so->so_pcb except where the
  pcb is actually used (i.e. cases where we don't return EOPNOTSUPP).

proposed on tech-net@
Use cross-cpp when extracting OpenSSL version.
Add missing includes, use new style function declarations.
return EOPNOTSUPP for pr_stat instead of returning success since we
don't fill in the struct stat passed to us.