GetBufferPointerv, GetBufferParameteri64v, and new values
for GetBufferParameteriv.

BUG=angle:565

Change-Id: I179a3193987b2bff1b0628e47f6a0d627541b0cf
Reviewed-on: https://chromium-review.googlesource.com/188203Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>