Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2015-11-17' into staging

QAPI patches

# gpg: Signature made Tue 17 Nov 2015 08:28:24 GMT using RSA key ID EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"

* remotes/armbru/tags/pull-qapi-2015-11-17:
  input: Document why x-input-send-event is still experimental
  qapi: Document introspection stability considerations

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>