This is necessary to support BSD command

VASliceParameterBufferH264.slice_data_bit_offset will point into the part
of slice header if there are some escaped bytes in the slice header. The offset
to slice data is needed for BSD unit so that BSD unit can fetch right slice data
for processing. This fixes conformance case BASQP1_Sony_C.jsv

The method to get the total number of bytes in the slice header is provided by Gwenole Beauchesne <gbeauchesne@splitted-desktop.com>

Some stress cases need a large BSD batch buffer.

The way to get drawable type is proposed by Gwenole Beauchesne <gbeauchesne@splitted-desktop.com>

Signed-off-by: Austin Yuan <shengquan.yuan@gmail.com>

Conflicts:
	va/x11/dri2_util.c

Signed-off-by: Austin Yuan <shengquan.yuan@gmail.com>

Signed-off-by: Austin Yuan <shengquan.yuan@gmail.com>

Fix libva-x11 dependencies. Ensure this grabs libva so that people don't have to check for that themselves.