Merge remote-tracking branch 'remotes/kraxel/tags/ui-20190201-pull-request' into...

Merge remote-tracking branch 'remotes/kraxel/tags/ui-20190201-pull-request' into staging

ui: fix build with SDL disabled, drop SDL1 support.

# gpg: Signature made Fri 01 Feb 2019 12:30:47 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-20190201-pull-request:
  ui: remove support for SDL1.2 in favour of SDL2
  hw/display/milkymist-tmu2: Move inlined code from header to source
  hw/display/milkymist-tmu2: Explicit the dependency to both X11 / OpenGL
  configure: LM32 Milkymist Texture Mapping Unit (tmu2) also depends of X11
  hw/display: Move Milkymist specific hardware out of common-obj list

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