libvpx

Allow for re-encoding frame if high overshoot.

For 1 pass CBR mode under screen content mode:
if pre-analysis (source temporal-sad) indicates significant
change in content, then check the projected frame size after
encode_frame(), and if size is above threshold, force re-encode
of that frame at max QP.

Change-Id: I91e66d9f3167aff2ffcc6f16f47f19f1c21dc688