Any conversions fix for RGB 3 bytes.  Fix for overread valgrind.  Avoid memcpy.  Add _Any unittests for all conversions.
BUG=121
TEST=./libyuv_unittest --gtest_filter=*Any
Review URL: https://webrtc-codereview.appspot.com/873010

git-svn-id: http://libyuv.googlecode.com/svn/trunk@401 16f28f9a-4ce2-e073-06de-1de4eb20be90