Libraries, or general-purpose tools or generally available free
    programs which are used unmodified in performing those activities but
    which are not part of the work.  For example, Corresponding Source
    includes interface definition files associated with source files for
    the work, and the source code for shared libraries and dynamically
    linked subprograms that the work is specifically designed to require,
    such as by intimate data communication or control flow between those
    subprogr