Libyuv: 1. Dividing gyp file to test and source. 2. Updating DEPS file to build tests (not only library). 
Review URL: http://webrtc-codereview.appspot.com/210001

git-svn-id: http://libyuv.googlecode.com/svn/trunk@13 16f28f9a-4ce2-e073-06de-1de4eb20be90