Currently when we poll a file descriptor, we only process EPOLLIN events
and if a connection is closed the receiving side has no means to deal with
it.
Add a callback for EPOLL{RD}HUP events and the default implementation for
these events that removes the file descriptor from epoll and closes it.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>