ui: opengl updates for dma-buf support.

# gpg: Signature made Tue 17 Oct 2017 12:13:36 BST
# 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>"
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* remotes/kraxel/tags/opengl-20171017-pull-request:
  egl-headless: add dmabuf support
  egl-helpers: add egl_texture_blit and egl_texture_blend
  egl-helpers: add dmabuf import support
  opengl: add flipping vertex shader
  opengl: move shader init from console-gl.c to shader.c
  console: add support for dmabufs

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