57785538c6 change the test for FreeBSD
from __FreeBSD_version to __FreeBSD__. However this test was performed
before sys/param.h was included, therefore __FreeBSD_version was never
defined. As the test was never true opt_random_ip_id.h was never included.
Submitted by: bdragon
Reported by: bdragon
MFC after: 1 week
X-MFC with: 57785538c6