This adds some missing CSR_* register macros, and documents some as being
priv v1.9.1 specific.
Backports commit 8e73df6aa3f2f0e5c26c03a94a88406616291815 from qemu
This ports over the RISC-V architecture from Qemu. This is currently a
very barebones transition. No code hooking or any fancy stuff.
Currently, you can feed it instructions and query the CPU state itself.
This also allows choosing whether or not RISC-V 32-bit or RISC-V 64-bit
is desirable through Unicorn's interface as well.
Extremely basic examples of executing a single instruction have been
added to the samples directory to help demonstrate how to use the basic
functionality.
