On FreeBSD the sysmbol __FreeBSD_kernel__ is only defines if a
specific param.h file is included, unlike Debian/kFreeBSD where this
symbol is always defined.  So also compile the FreeBSD specific code
if __FreeBSD__ is defined for FreeBSD 11 & 12 compatibility.
Signed-off-by: Christopher Hall <hsw@ms2.hinet.net>