Integrate 4.4BSD-Lite2 changes to IOC_* definitions

Bring in the long-overdue 4.4BSD-Lite2 rev 8.3 by cgd of
sys/ioccom.h. This uses UL suffix for the IOC_* constants so they
don't sign extend. Also bring in the handy diagram from NetBSD's
version of this file. This alters the 4.4BSD-Lite2 code slightly
in a way that's semantically the same but more compact.

This should stop the warnings from Chrome for bogus sign extension.

Reviewed by: kib@, jhb@
Differential Revision: https://reviews.freebsd.org/D26423