libvpx

Apply fast motion search to golden reference frame

This commit enables the rtc coding mode to run integral projection
based motion search for golden reference frame. It improves the
speed -6 compression performance by 1.1% on average, 3.46% for
jimred_vga, 6.46% for tacomascmvvga, and 0.5% for vidyo clips. The
speed -6 is about 6% slower.

Change-Id: I0fe402ad2edf0149d0349ad304ab9b2abdf0c804