Fix issue #131 : Fixed unreliable clock setting.
Turn clock and off by calling SetSyncSource on filter graph manager (as specifically recommended by MSDN DirectShow documentation), not calling SetSyncSource on individual filters 

git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@195 c2f33eb2-41b2-391d-4cb4-d9d0608729ba