Fix for SAO band offset merge cost calculation.
Fix for SAO band offset merge cost calculation.

Gives a tiny improvement to both bit rate and psnr.

ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar,lu-zero/kvazaar,lu-zero/kvazaar,lu-zero/kvazaar