Decision to scale down/up is based on buffer state and average QP
over previous time window. Limit the total amount of down-scaling
to be at most one scale down for now.
Reset certain quantities after resize (buffer level, cyclic refresh,
rate correction factor).
Feature is enable via the setting rc_resize_allowed = 1.
Change-Id: I9b1a53024e1e1e953fb8a1e1f75d21d160280dc7
d77f51ba9e