Coalesce rows by changing width/height and dropping into code instead of recursing.  Improve coalesce by setting stride to 0 so it can be used even on odd width images.  Reduce unittests to improve time to run emulators.
BUG=277
TEST=unittests all build and pass
R=ryanpetrie@google.com

Review URL: https://webrtc-codereview.appspot.com/2589004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@819 16f28f9a-4ce2-e073-06de-1de4eb20be90