with poll(2) after shutdown(SHUT_RD) has been called on the local side.
* poll.cc (poll): Use POSIX type nfds_t for second parameter. Drop
special socket handling for POLLIN. Add comment to explain why.
* include/sys/poll.h: Declare nfds_t. Use as type for second parameter
in poll(2) declaration.
if fd is invalid. Return POLLERR for each valid fd if cygwin_select
returned with error.
include/sys/poll.h: Change POLLERR comment according to above change.