2001-07-10  Lutz Müller <urc8@rz.uni-karlsruhe.de>

        * src/workbook-control-gui.c: Add a menu item "Send" to the file menu.
        If this one is clicked, pop up an Evolution-Composer with current
        workbook attached.
        * src/file-priv.h: New virtual function for GnumFileSaver:
        save_to_stream.
        Introduce GnumFileSaverSaveToStreamFunc. Keep a mime type.
        * src/file.[c,h]: Implement save_to_stream and mime_type detection.
        * src/gui-file.[c,h]: Reduce copy & paste by introducing
        (make_format_chooser) and (check_multiple_sheet_support_if_needed).
        New function: (gui_file_save_to_stream) which asks for the desired
        mime type.
        * src/bonobo-io.c: This file saver doesn't support save_to_stream.
        * src/stf.c: This one either.
        * src/xml-io.[c,h]: Implement save_to_stream.
        * src/plugin-service.c: Pass NULL for save_to_stream.