Enable background detection for adaptive quantizer control

Enable background detection for adaptive quantizer control

This commit enables a background detection approach for adaptive
quantizer control. It combines the cyclic refresh pattern and the
background information to determine the segment id for adaptive
quantizer selection, prior to the non-RD mode decision process.
It hence allows proper quantization information update for a more
precise rate-distortion modeling in the non-RD mode decision.

The compression performance of speed -5 for rtc set is improved
by 2.5%, at no speed change.

Change-Id: Ic3713e8ed9185b403b5b1679d19dabd57506d452