Teach poll(2) to support Linux-style POLLRDHUP events for sockets, if
requested. Triggered when the remote peer shuts down writing or closes
its end.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D29757
to then try to reproduce a kernel panic, which turned out to be a
race condition and hard to test from here.
Commit the changes anywhere as the "bind zero" case was a surprise
to me and we should try to maintain this status.
Also it is easy examples someone can build upon.
With help from: markj
Event: Waterloo Hackathon 2019
