Implement GLX_EXT_buffer_age for DRI2

[Dave Airlie]

On 19 January 2015 at 21:00, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> In order to suport GLX_EXT_buffer_age in DRI2, we need to pass back the
> last swap buffer count that the back buffer was defined for. For
> simplicity, we can reuse an existing field in the DRI2GetBuffers reply
> that is not used by current drivers, the flags. Since we change the
> interpretation of this flag, we also declare the semantic change with a
> DRI2 parameter and depend upon the DDX to enable the change
> responsibility (which is just a matter of reviewing whether the flags
> field has ever been used for a non-zero value).
>

This is just missing the why do we need to add this to DRI2 when we
have DRI3/Present that should be solving it.

Doesn't dri3 already do this?

Dave.