The test suite uses the standard automake support. Tests are always built,
but run only when you do a "make check".

Trying to optimize out the case where items_[i]. events is 0 would
result in a bogus pollfds[i]. Similarly in the select()-based impl,
while not strictly necessary it's better to get ZMQ_FD even if
events is 0 since that detects ETERM and friends.

Rewrite the select()-based zmq_poll() implementation to use
ZMQ_FD and ZMQ_EVENTS.

Also fix some corner cases: We should not pollute revents with
unrequested events, and we don't need to poll on ZMQ_FD at all
if a pollitem with no events set was passed in.

Dunno where those <TAB>s came from...

Rewrite zmq_poll() to use ZMQ_FD and ZMQ_EVENTS introduced on the
wip-shutdown branch. Only do the poll()-based version of zmq_poll (), the
select()-based version will not compile at the moment.