Add ROI support for VP9.

Add ROI support for VP9.

Extended ROI struct suitable for VP9.
ROI input from user is passed into internal struct and applied on every frame
(except key frame).

Enabled usage of all 4 VP9 segment features (delta_qp, delta_lf, skip,
ref_frame) via the ROI map input.
Made changes to nonrd_pickmode for the ref_frame feature.

Only works for realtime speed >= 5.
AQ_MODE needs to be turned off for ROI to take effect.

Change example in the sample encoder: vpx_temporal_svc_encoder.c to be suitable
for VP9.
Add datarate test.

Bump up ABI version.

BUG=webm:1470

Change-Id: I7e0cf6890649adb98a5fda2efb6ae1fa511c7fc9