Interpret the kqueue() close event correctly on epoll_wait().

On FreeBSD, we simulate epoll_* using kevents. Looks like epoll channel
descriptor going aways doesn't have same semantics on FreeBSD (kqueue()
descriptor going away).

Specifically, after epoll_wait(), event->data.ptr=NULL means kqueue descriptor
went away. tirpc code was trying to dereference this NULL pointer resulting in
segfault.
epoll tracing.
packed pre-processor pragma changes.