Syntax:  bf(%debug) nl() 
           Provide tt(parse()) and its support functions with debugging code,
            showing the actual parsing process on the standard output
            stream. When included, the debugging output is active by default,
            but its activity may be controlled using the bf(setDebug(bool
            on-off)) member. Note that no tt(#ifdef DEBUG) macros are used
            anymore. Rerun b() without the bf(--debug) option to generate an
            equivalent parser not containing the debugging code. 
