- Introduce a new ioctl, DRM_IOCTL_SET_VERSION. This ioctl allows the

    server or client to notify the DRM that it expects a certain version of
    the device dependent or device independent interface. If the major
    doesn't match or minor is too large, EINVAL is returned. A major of -1
    means that the requestor doesn't care about that portion of the
    interface. The ioctl returns the actual versions in the same struct.
- Introduce DRM DI interface version 1.1. If the server requests version
    1.1, then the DRM sets the unique itself according to the busid of the
    device it probed, which may then be accessed as normal using getunique.
- Request version 1.1 in libdrm's drmOpenByBusID, allowing the X Server to
    request based on a BusID. Introduce a wrapper for DRM_IOCTL_SET_VERSION
    and bump libdrm minor version.
- Pass the busid in DRIScreenInit if libdrm can handle both a busid and
    name. This allows drmOpenByBusID to be used to find the DRM instead of
    just the driver name, which allows us in the future to tie a DRM more
    strongly to the device it probed to. Introduce a function
    DRICreatePCIBusID which creates a busid in the form pci:oooo:bb:dd.f
    similar to linux's pci_name() function. This matches the format used by
    the DRM in version 1.1. libdrm knows how to match both this format and
    the old PCI:b:d:f format.
- Use the new DRICreatePCIBusID function in the *_dri.c to request the new,
    more exact busid format.