- Disallow < 1 values for SO_SNDBUF, SO_RCVBUF, SO_SNDLOWAT, and
SO_RCVLOWAT; return EINVAL if the user attempts to set <= 0.
Inspired by PR #3770, from Havard Eidnes <he@vader.runit.sintef.no>.
- For SO_SNDLOWAT and SO_RCVLOWAT, don't let the low-water mark get
set above the high-water mark. Behavior is now consistent with
BSD/OS: If such an attempt is made, silently truncate to the high-water
value.