Stereo 3D v3

[Damien Lespiau]

Follow up of:
 http://lists.freedesktop.org/archives/dri-devel/2012-September/028278.html

Let's try again! This time, intead of a magic connector property to select if
we want to return more modeinfo flags to userspace, this series introduces a
new SET_CAP ioctl.

So the flow goes as following:
  1/ the DRM client (limited to the DRM master) can notify it knows about those
     flags through SET_CAP
  2/ we parse the HDMI CEA vendor blog for 3D_Present and patch the mandatory
     modes with the layouts they support (in ->flags)
  3/ we can then handle a modeset with one (and only one) of those stereo 3D
     layout set on the mode. This includes writing a vendor infoframe with
     the information about the layout we're sending

libdrm patches will follow with a new drmSetCap() function and the stereo 3D
flags.

Testing has been done with intel-gpu-tools' testdisplay that can now compose a
left and right image for the "top and bottom", "side by side half" and "frame
packing" stereo 3d layouts (patches posted on intel-gfx).