Merge remote-tracking branch 'remotes/kraxel/tags/pull-sdl-2' into staging

sdl2: mouse wheel support, ui config notify

# gpg: Signature made Tue 29 Apr 2014 11:17:01 BST using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/kraxel/tags/pull-sdl-2:
  sdl2: Support mouse wheel
  sdl2: add ui info setting.

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