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 that creates and tears down route sockets,
and confirms that only SOCK_RAW works with socket(), and nothing works
with socketpair().