FSF gcc-4.x for Atmel AVR cross-development

Included is the basic C++ compiler, although this is only of limited
use without a libstdc++.

Supported debugging formats: -gdwarf-2 [default], -gstabs

Locally added support for the following AVR devices:

  ATmega64RFR2, ATmega644RFR2, ATmega128RFR2, ATmega1284RFR2,
  ATmega256RFR2, ATmega2564RFR2

See also: https://gcc.gnu.org/