Teach gcc41 about %b and %D taking two parameters in a better way.

Teach gcc41 about %b and %D taking two parameters in a better way.

Previously, we had special code to handle the properties of %b and %D
(which are for printing bit masks and hexdumps, respectively). Remove
this code and instead use chained format_char_info's to pass the
information that both of these formats consume two arguments.