Replace division with bit shift in choose_partitioning
Replace division with bit shift in choose_partitioning

This commit explicitly uses the bit shift operation instead of
division for computing block variance.

Change-Id: Id19c0ff27dd1d1ae4aceee6657e1aad0d406bd74

pcwalton/libvpx,iniwf/webm.libvpx,kalli123/webm.libvpx,matanbs/vp982,Laknot/libvpx,matanbs/vp982,ittiamvpx/libvpx-1,Acidburn0zzz/webm.libvpx,shareefalis/libvpx,matanbs/webm.libvpx,shacklettbp/aom,reimaginemedia/webm.libvpx,matanbs/webm.libvpx,openpeer/libvpx_new,shyamalschandra/libvpx,shacklettbp/aom,lyx2014/libvpx_c,gshORTON/webm.libvpx,matanbs/webm.libvpx,kim42083/webm.libvpx,Topopiccione/libvpx,GrokImageCompression/aom,reimaginemedia/webm.libvpx,thdav/aom,gshORTON/webm.libvpx,zofuthan/libvpx,mwgoldsmith/libvpx,shyamalschandra/libvpx,liqianggao/libvpx,charup/https---github.com-webmproject-libvpx-,kim42083/webm.libvpx,Laknot/libvpx,hsueceumd/test_hui,pcwalton/libvpx,kleopatra999/webm.libvpx,reimaginemedia/webm.libvpx,ittiamvpx/libvpx-1,Acidburn0zzz/webm.libvpx,luctrudeau/aom,thdav/aom,hsueceumd/test_hui,ittiamvpx/libvpx-1,matanbs/vp982,matanbs/vp982,jmvalin/aom,mwgoldsmith/libvpx,gshORTON/webm.libvpx,matanbs/webm.libvpx,mbebenita/aom,openpeer/libvpx_new,zofuthan/libvpx,webmproject/libvpx,mwgoldsmith/vpx,jmvalin/aom,Acidburn0zzz/webm.libvpx,lyx2014/libvpx_c,Acidburn0zzz/webm.libvpx,openpeer/libvpx_new,gshORTON/webm.libvpx,GrokImageCompression/aom,altogother/webm.libvpx,felipebetancur/libvpx,abwiz0086/webm.libvpx,mbebenita/aom,pcwalton/libvpx,Topopiccione/libvpx,goodleixiao/vpx,mwgoldsmith/vpx,webmproject/libvpx,reimaginemedia/webm.libvpx,mwgoldsmith/libvpx,abwiz0086/webm.libvpx,stewnorriss/libvpx,shareefalis/libvpx,jacklicn/webm.libvpx,kalli123/webm.libvpx,zofuthan/libvpx,kalli123/webm.libvpx,lyx2014/libvpx_c,smarter/aom,hsueceumd/test_hui,jdm/libvpx,shacklettbp/aom,liqianggao/libvpx,abwiz0086/webm.libvpx,gshORTON/webm.libvpx,Maria1099/webm.libvpx,mwgoldsmith/vpx,kim42083/webm.libvpx,altogother/webm.libvpx,running770/libvpx,ShiftMediaProject/libvpx,shareefalis/libvpx,luctrudeau/aom,liqianggao/libvpx,VTCSecureLLC/libvpx,jdm/libvpx,mbebenita/aom,luctrudeau/aom,mbebenita/aom,kim42083/webm.libvpx,jdm/libvpx,thdav/aom,Acidburn0zzz/webm.libvpx,VTCSecureLLC/libvpx,Distrotech/libvpx,jdm/libvpx,shacklettbp/aom,stewnorriss/libvpx,Suvarna1488/webm.libvpx,felipebetancur/libvpx,zofuthan/libvpx,Topopiccione/libvpx,liqianggao/libvpx,ShiftMediaProject/libvpx,shyamalschandra/libvpx,felipebetancur/libvpx,stewnorriss/libvpx,goodleixiao/vpx,ittiamvpx/libvpx-1,mbebenita/aom,Distrotech/libvpx,mwgoldsmith/libvpx,Maria1099/webm.libvpx,Laknot/libvpx,charup/https---github.com-webmproject-libvpx-,lyx2014/libvpx_c,openpeer/libvpx_new,altogother/webm.libvpx,thdav/aom,Suvarna1488/webm.libvpx,kalli123/webm.libvpx,webmproject/libvpx,jmvalin/aom,shareefalis/libvpx,mwgoldsmith/libvpx,mbebenita/aom,shacklettbp/aom,VTCSecureLLC/libvpx,Suvarna1488/webm.libvpx,hsueceumd/test_hui,webmproject/libvpx,lyx2014/libvpx_c,goodleixiao/vpx,Maria1099/webm.libvpx,luctrudeau/aom,kleopatra999/webm.libvpx,gshORTON/webm.libvpx,iniwf/webm.libvpx,iniwf/webm.libvpx,shareefalis/libvpx,thdav/aom,hsueceumd/test_hui,kalli123/webm.libvpx,mwgoldsmith/vpx,ittiamvpx/libvpx-1,GrokImageCompression/aom,iniwf/webm.libvpx,reimaginemedia/webm.libvpx,VTCSecureLLC/libvpx,matanbs/vp982,Maria1099/webm.libvpx,stewnorriss/libvpx,webmproject/libvpx,jdm/libvpx,Laknot/libvpx,smarter/aom,mwgoldsmith/vpx,charup/https---github.com-webmproject-libvpx-,iniwf/webm.libvpx,charup/https---github.com-webmproject-libvpx-,lyx2014/libvpx_c,smarter/aom,matanbs/vp982,ittiamvpx/libvpx-1,shyamalschandra/libvpx,VTCSecureLLC/libvpx,jacklicn/webm.libvpx,matanbs/webm.libvpx,ShiftMediaProject/libvpx,mbebenita/aom,reimaginemedia/webm.libvpx,Distrotech/libvpx,goodleixiao/vpx,kalli123/webm.libvpx,jacklicn/webm.libvpx,altogother/webm.libvpx,Distrotech/libvpx,luctrudeau/aom,Topopiccione/libvpx,liqianggao/libvpx,liqianggao/libvpx,running770/libvpx,zofuthan/libvpx,webmproject/libvpx,Maria1099/webm.libvpx,abwiz0086/webm.libvpx,running770/libvpx,running770/libvpx,kim42083/webm.libvpx,Topopiccione/libvpx,kleopatra999/webm.libvpx,matanbs/webm.libvpx,pcwalton/libvpx,GrokImageCompression/aom,openpeer/libvpx_new,smarter/aom,ShiftMediaProject/libvpx,zofuthan/libvpx,shareefalis/libvpx,Distrotech/libvpx,Suvarna1488/webm.libvpx,altogother/webm.libvpx,kim42083/webm.libvpx,Laknot/libvpx,mbebenita/aom,shacklettbp/aom,abwiz0086/webm.libvpx,shyamalschandra/libvpx,shyamalschandra/libvpx,thdav/aom,luctrudeau/aom,mwgoldsmith/vpx,GrokImageCompression/aom,Laknot/libvpx,altogother/webm.libvpx,abwiz0086/webm.libvpx,stewnorriss/libvpx,pcwalton/libvpx,goodleixiao/vpx,VTCSecureLLC/libvpx,stewnorriss/libvpx,pcwalton/libvpx,kleopatra999/webm.libvpx,smarter/aom,kleopatra999/webm.libvpx,matanbs/vp982,Suvarna1488/webm.libvpx,Maria1099/webm.libvpx,Topopiccione/libvpx,jmvalin/aom,jacklicn/webm.libvpx,hsueceumd/test_hui,ShiftMediaProject/libvpx,felipebetancur/libvpx,charup/https---github.com-webmproject-libvpx-,charup/https---github.com-webmproject-libvpx-,mwgoldsmith/libvpx,jacklicn/webm.libvpx,running770/libvpx,mbebenita/aom,jmvalin/aom,Acidburn0zzz/webm.libvpx,Distrotech/libvpx,felipebetancur/libvpx,running770/libvpx,openpeer/libvpx_new,jacklic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