libvpx

Choosing GOOD mode by default.

This patch fixes slow first pass problem. Mode could only be determined
from the deadline value during frame encode call. Unfortunately, we use
mode value before any encode calls during the first pass encoding (see
set_speed_features() logic). The mode for the first pass must be different
from BEST to make first pass fast.

Change-Id: I562a7d32004ff631695d91c09a44d8a9076fd6b5