Cherrypick so we can publish N version code description ASAP

Fix issue #30766518: Document what targeting N does

Also small documentation cleanup in a few other places.

(cherry picked from commit b34cbedb4e36f184232d7f40b093bdc9fd0cd752)

Change-Id: I9560b29faa4f2674277349272af8193122a1f95e
4 files changed