Port alt reference frame filter improvement to VP9
Port alt reference frame filter improvement to VP9

Use sharp filter to generate motion compensated reference for
temporal filtering. It improves the average coding performance of
VP9 speed 0:
derf    0.34%
hevcmr  0.38%
stdhd   0.58%

Change-Id: I1772a051be545de8c343055274e5ca0929d19cda

mwgoldsmith/vpx,luctrudeau/aom,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,webmproject/libvpx,Topopiccione/libvpx,mbebenita/aom,webmproject/libvpx,smarter/aom,webmproject/libvpx,mwgoldsmith/libvpx,GrokImageCompression/aom,mwgoldsmith/vpx,mbebenita/aom,mbebenita/aom,webmproject/libvpx,webmproject/libvpx,mwgoldsmith/libvpx,ittiamvpx/libvpx-1,luctrudeau/aom,ittiamvpx/libvpx-1,mbebenita/aom,ShiftMediaProject/libvpx,mbebenita/aom,mbebenita/aom,smarter/aom,mwgoldsmith/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,mwgoldsmith/libvpx,smarter/aom,smarter/aom,Topopiccione/libvpx,mbebenita/aom,luctrudeau/aom,mwgoldsmith/vpx,luctrudeau/aom,ShiftMediaProject/libvpx,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,Topopiccione/libvpx,ittiamvpx/libvpx-1,GrokImageCompression/aom,mwgoldsmith/vpx,ittiamvpx/libvpx-1,luctrudeau/aom,webmproject/libvpx,mwgoldsmith/libvpx,mbebenita/aom,ittiamvpx/libvpx-1,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mbebenita/aom,ittiamvpx/libvpx-1,GrokImageCompression/aom,GrokImageCompression/aom,Topopiccione/libvpx,GrokImageCompression/aom,smarter/aom,ShiftMediaProject/libvpx,Topopiccione/libvpx