BUG=none
TESTED=libyuv_unittest
R=fbarchard@google.com

Review URL: https://webrtc-codereview.appspot.com/16259004/

the benckmarking result is as follows:
toolchain: gcc 4.9
hardware: A53

| count | C Times/NEON times |
| 16    | 3.35               |
| 128   | 6.63               |
| 512   | 7.47               |
| 1024  | 7.72               |

Change-Id: Ic10bf22d77d069a1a2074b68bd5a310c579ec490

Review URL: https://webrtc-codereview.appspot.com/21159004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1043 16f28f9a-4ce2-e073-06de-1de4eb20be90