Merge remote-tracking branch 'remotes/kraxel/tags/pull-gtk-20150529-1' into staging

gtk: add opengl rendering support.
small bugfixes for gtk and opengl ui code.

# gpg: Signature made Fri May 29 10:44:54 2015 BST using RSA key ID D3E87138
# 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>"

* remotes/kraxel/tags/pull-gtk-20150529-1:
  gtk: Replace gdk_cursor_new()
  gtk: add opengl support, using egl
  ui: add egl-helpers
  ui: shader.h protect against double inclusion
  ui: use libexpoxy

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