Merge remote-tracking branch 'remotes/kraxel/tags/ui-20200520-pull-request' into...

ui: windows keyboard fixes for gtk & sdl.
ui: require GTK 3.22 or newer.

# gpg: Signature made Wed 20 May 2020 09:41:48 BST
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/ui-20200520-pull-request:
  ui: increase min required GTK version to 3.22.0
  ui/gtk: use native keyboard scancodes on Windows
  ui/gtk: don't pass on win keys without keyboard grab
  ui/sdl2-input: use trace-events to debug key events
  ui/sdl2: start in full screen with grab enabled
  ui/sdl2: fix handling of AltGr key on Windows
  ui/gtk: remove unused variable ignore_keys
  ui/gtk: remove unused code
  ui/gkt: release all keys on grab-broken-event
  ui/gtk: fix handling of AltGr key on Windows
  ui/win32-kbd-hook: handle AltGr in a hook procedure

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