Upgrade AVR-GCC to GCC 3.4.1.

Also included is a local hack to allow for 0bXXX binary constants,
since this appears to be a frequently requested item in the AVR
developers community.

The GCC configuration is tuned to allow for both, -gstabs [the default
if only -g is given], and -gdwarf-2 debugging options. ELF/DWARF-2 is
the emerging format as promoted by Atmel, and is intented to be
directly usable in their AVR Studio simulator in future. Eventually,
AVR-GDB will fully support DWARF-2 debugging as well some day.