drm tiled monitor support (not hiding in kernel)

So I believe attempts to hide the DP MST tiled monitors in the kernel, are a path to failure, so I've resurrected my previous code to just create a tile property on the connectors for userspace to key off.

The contents of the tile blob are ABI, and I expect it to be parsed by a fair few userspace projects.

So far I've ported a few pieces of GNOME to using it and posted patches for that to their lists,

The X server should use this for make better XINERAMA info, but otherwise drivers should pass the TILE property through to the clients, as it contains nothing kernel specific.

Dave.