*   Fix FTRL L2-shrinkage behavior: the gradient from the L2 shrinkage term
        should not end up in the accumulator.
    *   Fix toco compilation/execution on Windows.
    *   GoogleZoneProvider class added to detect which Google Cloud Engine zone
        tensorflow is running in.
    *   It is now safe to call any of the C API's TF_Delete\* functions on
        nullptr.
    *   Log some errors on Android to logcat.