Build fixes for recent FreeBSD -current

Build fixes for recent FreeBSD -current

Let's try a new paradigm of using flag checks in the main code,
which are based off of precise version checks in the FreeBSD-specific
param.h file.  It's not quite configure checks, but is much more
granular.

Change-Id: I8274a8ad3747d3847cdec3ce8d521837fd5b2a92
Reviewed-on: http://gerrit.openafs.org/11467
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>