32-bit and 64-bit RISC-V using GCC

• The port automatically configures itself for 32-bit and 64-bit RISC-V architectures on basis of #defines set by GCC.
• The demo application runs on the spike simulator in 64-bit mode, and needs the riscv GCC compiler and spike simulator to be installed somewhere for the build to succeed.
• The tarball contains a subtree of the FreeRTOS 8.2.3 ZIP, which is sufficient (apart from GCC+spike) to build and run the demo app.

Contributed to the project by Technolution B.V. (www.technolution.nl)!