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)

Add a simple regression test for stream UNIX domain sockets and the
bind()/connect() system calls, which is intended to confirm that the
right successes and errors occur when rendezvousing via the file system
name space.