YUY2 and UYVY to ARGB had oversampling bug.  This passes 0 for UV stride, avoiding the issue.  A better solution would be a version of the conversions that does not do 2 rows subsampled.  But the performance would only be slightly faster.
BUG=76
TEST=build\release\libyuv_unittest.exe --gtest_catch_exceptions=0 --gtest_filter=*UY*ToARGB*
Review URL: https://webrtc-codereview.appspot.com/773004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@333 16f28f9a-4ce2-e073-06de-1de4eb20be90