configure: check for EFD_NONBLOCK | EFD_CLOEXEC flags

Add check for the EFD_NONBLOCK and EFD_CLOEXEC flags to the
CONFIG_EVENTFD test.
This fixes the following build failure on Fedora 9:

      CC    event_notifier.o
    event_notifier.c: In function `event_notifier_init':
    event_notifier.c:21: error: `EFD_NONBLOCK' undeclared (first use in this function)
    event_notifier.c:21: error: (Each undeclared identifier is reported only once
    event_notifier.c:21: error: for each function it appears in.)
    event_notifier.c:21: error: `EFD_CLOEXEC' undeclared (first use in this function)
    make: *** [event_notifier.o] Error 1

Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
