Add amd64 subtarget for OpenBSD

Add amd64 subtarget for OpenBSD

The subtarget name is amd64_obsd.  A sysname is created for the
OpenBSD 4.5 release, since it's current.  The sysname id range starting at
4000 is claimed for amd64_obsd, with amd64_obsd45 at 4014, so that prior
releases can be added in the correct order, if needed.

Mention of Jim Rees and CITI in new param file changed to line crediting
them for original work.

Reviewed-on: http://gerrit.openafs.org/http://gerrit.openafs.org/153
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>