remove sstream from videocommon

BUG=16
TESTED=builds ok without it
Review URL: https://webrtc-codereview.appspot.com/426005

git-svn-id: http://libyuv.googlecode.com/svn/trunk@198 16f28f9a-4ce2-e073-06de-1de4eb20be90

source/video_common.cc

@@ -11,8 +11,6 @@
 
 #include "libyuv/video_common.h"
 
-#include <sstream>
-
 #ifdef __cplusplus
 namespace libyuv {
 extern "C" {