Add an isTrickleRestart flag to the Invalidation class.  The restarted flag is
documented for internal use only. The flag is required on construction and
preserved when converting to and from InvalidationP.



git-svn-id: http://google-cache-invalidation-api.googlecode.com/svn/trunk@258 1cc9d426-c294-39be-ba72-c0199ca0f247