HPCC-9415 Use epoll, add EPOLLRDHUP define for Centos5.x

Also fix Windows build break

Signed-off-by: Mark Kelly <mark.kelly@lexisnexis.com>
Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge branch 'hpcc9415x' into candidate-4.2.0

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>