Progress in support for the riscv64 platform

Since ourprevious report,there has been significant progress on support for riscv64:

• There's now aweb page for the platform,with details of (broadened) hardware support (for those lucky/deserving enoughto have hardware, of course).
• Followingsomecommitsfrom Dale Rahn (drahn@),install setsnow include xenocara.

As always, thanks to those involved!