libvpx

aq-mode=3: Reduce boost for segment#2 at low bitrates/low res.

Reduce boost for segment#2 for low bitrates and low-res.

This change is to reduce the rate overshoot at low bitrates.
No change in behavior, except at the very low bitrates.

Change-Id: I0dbd9d3b6356da5804de94adf10fca6a7a8f8948