Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Test the poll(2) return value.

MFC after: 2 weeks

Test suite for the poll(2)/select(2) on fifos, pipes and sockets,
and recorded results for several operating systems.

Submitted by: bde
Approved by: re (kensmith)