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 the undocumented -R option to disable randomness for regression-testing.

Add a couple of simple regression tests accessible with "make test", they
depend on the md(4) driver.

FYI I have also tried running the test against a week old newfs and it
passed.