- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

- Handle an interrupt for csa primarily in the bridge driver,
then invoke the children. As the value of HISR can be read
only once, pass the HISR to the children via struct
csa_bridgeinfo, stored in the ivars of them.
- Clear the contents of serial FIFO upon stopping the DMA for
playing. This may eliminate buzz on playing. Experimental.

- Introduce the bridge drivers for Sound Blaser, GUS and Crystal
Semiconductor CS461x/428x.
- Add support for GUS and CS461x/428x pcm.

Bridges reviewed by: dfr, cg
GUS non-PnP support submitted by: Ville-Pertti Keinonen <will@iki.fi>
GUS PnP support tested by: Michiru Saito <mich@mtci.ne.jp>