scale to 3/4 bug fix for odd widths.  multiply to index into source by scale factor should be 4 / 3 not 3 / 4.
BUG=433
TESTED=set LIBYUV_WIDTH=1276 out\release\libyuv_unittest.exe --gtest_catch_exceptions=0 --gtest_filter=*.Scale*
R=tpsiaki@google.com

Review URL: https://webrtc-codereview.appspot.com/49219004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1391 16f28f9a-4ce2-e073-06de-1de4eb20be90