Merge remote-tracking branch 'remotes/kraxel/tags/ui-20201211-pull-request' into staging

ui/console ui_info tweaks.
ui/vnc: alpha cursor support.
ui/vnc: locking fixes.
ui/sdl: add extra mouse buttons.

# gpg: Signature made Fri 11 Dec 2020 09:12:39 GMT
# 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-20201211-pull-request:
  sdl2: Add extra mouse buttons
  ui/vnc: Add missing lock for send_color_map
  vnc: add alpha cursor support
  vnc: add pseudo encodings
  vnc: drop unused copyrect feature
  vnc: use enum for features
  console: allow con==NULL in dpy_{get, set}_ui_info and dpy_ui_info_supported
  console: drop qemu_console_get_ui_info

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