DRI2INFOREC_VERSION 6 introduces DRI2SwapLimit which enables us to schedule
swaps and retrieve next buffer n-times as given by the swap-limit. This
further enables us to do asynchronous swaps which enables asynchronous
rendering to n-buffers.

The swap limit is given by the xorg.conf option DRI2MaxBuffers. If
DRI2MaxBuffers is not specified no swap limit will be set and behavior will
default to synchronous swaps.

Notably, this commit bumps up the required DRI2INFOREC_VERSION to 5 as required
by drmAuth. DRI2INFOREC_VERSION 6, with DRI2SwapLimit, is optional.

Change-Id: Ia39dcd91628172f884eac914938d8ddd4b41aa71