Merge remote-tracking branch 'github-mike/dm-devel-cache-v3.9-dm-core-editing' into thin-dev

Conflicts:
	Documentation/device-mapper/cache.txt
[dm-cache] Add help paragraph to Kconfig
[dm-cache] Add Kcofig help for mq and cleaner policies.
[dm-cache] convert some c++ style comments to C
[dm-cache] whitespace
Merge branch 'thin-dev' into all-caches