clearUserDocs( [options] )
    Deletes user-defined documentation.

    Parameters
    ----------
    options: Object (optional)
    	Options.

    options.include: RegExp|ArrayLikeObject (optional)
    	Documentation inclusion filter.

    options.exclude: RegExp|ArrayLikeObject (optional)
    	Documentation exclusion filter.

    options.filter: string (optional)
        Filter type. This option is only applicable for array-like inclusion and
        exclusion filters. May be one of the following:

        -   'alias': filter based on documentation alias. If a filter matches a
        documentation alias, the user-defined documentation is removed.
        -   'value': filter based on object reference. If a filter matches an
        associated object reference, the user-defined documentation is removed.
        -   '*': filter based on both documentation alias and object reference.
        If a filter matches either a documentation alias or an associated object
        reference, the user-defined documentation is removed.

        Default: '*'.

    Examples
    --------
    > function foo() {};
    > userDoc( 'foo', foo, '\nfoo()\n    Foo bar.\n' );
    > help( foo )
    > clearUserDocs();
    > help( foo )

    See Also
    --------
    userDoc