- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r281923, r281924: Add link to mvs(4).

MFC r273457: Document sort_io_queue sysctls/tunables.

MFC r271926: Mention read_ahead tunables/sysctls.

MFC r262332 (by ivoras): Grammar fix

MFC r262294 (by ivoras):
Explain how and where kern.cam.ada.write_cache can be set in practical
situations.

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

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

Remove trailing whitespace per mdoc lint warning

Disussed with: gavin
No objection from: doc
Approved by: joel
MFC after: 3 days

Fix some Xr references:

- ada(4): ad(4) - removed, ada(4) would be a self-referencing entry
- cd(4): ad(4) -> ada(4)
- da(4): ad(4) -> ada(4)
- DEVICE_PROBE(9): ugen(5) -> ugen(4)
- ed(4): dhclinet(8) -> dhclient(8) (typo)
- lmc(4): Netgraph(4) -> netgraph(4)
- security(7): rc.conf(8) -> rc.conf(5)
- sfxge(4): cpuset(8) -> cpuset(1)
- sbp(4): sysctl(1) -> sysctl(8)
- portindex(5): build(1) -> build(7)
- u3g(4): usbconfig(5) -> usbconfig(8)
- usb_quirk(4): usbconfig(5) -> usbconfig(8)

Found with: textproc/igor
MFC after: 3 days

- Add kern.cam.ada.X.write_cache tunables/sysctls to control write caching
on per-device basis.
- While adding support for per-device sysctls, merge from graid branch
support for ADA_TEST_FAILURE kernel option, which opens few more sysctl,
allowing to simulate read and write errors for testing purposes.

Fix spelling.

Make ada(4) driver to control device write cache, same as ata(4) does.
Add kern.cam.ada.write_cache sysctl/tunable to control it alike hw.ata.wc.

Bump .Dd due to additions in r214279.

MFC after: 3 days

Fix formatting.

Reported by: yongari

Add information about the values and default setting of the
kern.cam.ada.spindown_shutdown sysctl.

MFC after: 3 weeks

Mostly revert r203420, and add similar functionality into ada(4) since the
existing code caused problems with some SCSI controllers.

A new sysctl kern.cam.ada.spindown_shutdown has been added that controls
whether or not to spin-down disks when shutting down.
Spinning down the disks unloads/parks the heads - this is
much better than removing power when the disk is still
spinning because otherwise an Emergency Unload occurs which may cause damage
to the actuator.

PR: kern/140752
Submitted by: olli
Reviewed by: arundel
Discussed with: mav
MFC after: 2 weeks

Add links to cam(4).

Grammar and mdoc improvements.

MFC after: 3 days

Add ada(4) man page.