Syntax: bf(%scanner-class-name) tt(scannerClassName) nl() 
           Defines the name of the scanner class, declared by the tt(pathname)
            header file that is specified at the tt(scanner) option or 
            directive. By default the class name ttt(Scanner) is used.

It is an error if this directive is used and either the tt(scanner) directive
was not provided, or the parser class interface in an already existing parser
class header file does not declare a scanner class tt(d_scanner) object.

