Future of VAX back end in GCC has been saved

Another Bountysource campaign around the GCC project has been completed successfully [1].

The VAX backend in GCC has been converted to MODE_CC register representation [2] reducing the number of backends still using cc0 to two: AVR and CR16 [3]. For AVR, there is still a pending Bountysource campaign currently at $7,215.

All backends must be converted to MODE_CC prior the release of GCC 11 or they will be removed [5]. So, if AVR and CR16 are supposed to be supported by GCC in future releases, they need to be converted to MODE_CC register representation.

The VAX backend in GCC is used by VAX port of NetBSD and therefore essential for the port.

> [1] https://www.bountysource.com/issues/91495157-vax-convert-the...

> [2] https://gcc.gnu.org/wiki/CC0Transition

> [3] https://gcc.gnu.org/backends.html

> [4] https://www.bountysource.com/issues/84630749-avr-convert-the...

> [5] https://gcc.gnu.org/legacy-ml/gcc-patches/2019-09/msg01256.h...