libvpx

Added Prediction Filter to Mode Selection

Added the ability to optionally filter the prediction data
when inter modes are selected (excludes SPLITMV, for now).

The mode selection loop considers both the filtered and
non-filtered prediction data when choosing mode. The filter
can be turned on/off at the frame-level, or signaled for
each MB.

Change-Id: I1b783c71d95a361ab36c761b07e8a6b06bc36822