adding Sugar.Date.clone to externs
adding Sugar.Date.clone to externs


Former-commit-id: 90e12a5959059cf00e4eed64f88b689af00ede6a [formerly 98711b38ab2ce4a3f3ab2ea54aa6634890cead48]
Former-commit-id: 63b0c737704be3e924f539d483a037e07bc28622
andrewplummer/Sugar,andrewplummer/Sugar,romancow/Sugar,romancow/Sugar