Makes the thresholds for the multiframe quality enhancement module
depend on the difference between the base quantizers. Also modifies
the mixing function to weigh the current low quality frame less if
the difference in quantizer is large. With the above modifications
mfqe works well for both scalable patterns as well as low quality
key frames.
Change-Id: If24e94f63f3c292f939eea94f627e7ebfb27cb75
47dcd769c1