Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

- Comment a line which sets CISS_DEBUG by default.
- Use -DCISS_DEBUG rather than -DCISS_DEBUG=0.

Add the 'ciss' driver, which supports the Compaq SmartRAID 5* family of
RAID controllers (5300, 532, 5i, etc.)

Thanks to Compaq and Yahoo! for support during the development of this
driver.

MFC after: 1 week