Merge remote-tracking branch 'remotes/pmaydell/tags/pull-cocoa-20150925-1' into staging

cocoa queue:
 * fix stuck-key bug if keys were down when QEMU lost focus
 * prompt the user whether they really meant to quit
 * remove the 'open image file' dialog box we used to display
   if the user started QEMU without arguments

# gpg: Signature made Fri 25 Sep 2015 23:17:19 BST using RSA key ID 14360CDE
# gpg: Good signature from "Peter Maydell <peter.maydell@linaro.org>"
# gpg:                 aka "Peter Maydell <pmaydell@gmail.com>"
# gpg:                 aka "Peter Maydell <pmaydell@chiark.greenend.org.uk>"

* remotes/pmaydell/tags/pull-cocoa-20150925-1:
  ui/cocoa.m: remove open dialog code
  ui/cocoa.m: prevent stuck key situation
  ui/cocoa.m: verify with user before quitting QEMU

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