BountySource campaign to modernize the AVR back end in GCC

This is a BountySource campaign I created that aims at funding the work on the AVR backend in GCC so it can be converted from the cc0 to the MODE_CC register representation similar to the m68k backend.

Without this conversion work, the AVR backend would be removed in the GCC-11 development cycle.

Relevant links:

* m68k campaign: https://www.bountysource.com/issues/80706251-m68k-convert-th...

* GCC bug report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92729

* GCC wiki on cc0 transition: https://gcc.gnu.org/wiki/CC0Transition

* Deprecation notice for cc0: https://gcc.gnu.org/ml/gcc-patches/2019-09/msg01256.html

If you are interested in keeping the AVR backend in GCC-11 and beyond, please consider supporting this campaign with a one-time donation.