cppmain.c (do_preprocessing): New function; most of the old main.

cppmain.c (do_preprocessing): New function; most of the old main.

        * cppmain.c (do_preprocessing): New function; most of the old
        main.
        (main): Call it to do most of the work.
        (cb): Move from global scope to set_callbacks ().
        (setup_callbacks): Get the callback pointer.
        (general_init, printer_init): Clean up code and comments.

From-SVN: r39012