libvpx

Changes to auto partition size selection.

Changes to code to auto select a partition size range
based on data from spatial neighbors.

Now looks at the sb_type in each 8x8 block of above
and left SB64.

The effect on speed 1 is now weaker giving better
quality but less speed gain. Now also used in speed 2.

Change-Id: Iace33a97d5c3498dd2a9a8a4067351941abcbabc