align clangcl using declspec instead of gcc style vector BUG=451 TESTED=clang=1 build on windows [email protected] Review URL: https://webrtc-codereview.appspot.com/57549004 git-svn-id: http://libyuv.googlecode.com/svn/trunk@1425 16f28f9a-4ce2-e073-06de-1de4eb20be90