Merge remote-tracking branch 'remotes/kraxel/tags/ui-20180112-pull-request' into staging

sdl2: bugfixes.
spice: cleanups.
input: mem leak fix.
gtk: deprecate 2.x support.

# gpg: Signature made Fri 12 Jan 2018 14:52:39 GMT
# gpg:                using RSA key 0x4CB6D8EED3E87138
# 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>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/ui-20180112-pull-request:
  sdl2: Ignore UI hotkeys after a focus change when GUI modifier is held
  sdl2 uses surface relative coordinates
  sdl2: Do not hide the cursor on auxilliary windows
  spice: remove unused timer list
  spice: remove only written event_mask field
  spice: remove unused watch list
  spice: remove QXLWorker interface field
  ui: deprecate use of GTK 2.x in favour of 3.x series
  input: fix memory leak

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