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.
Add code to insert calls to a helper function to do the stack
limit checking when we handle these forms of instruction
that write to SP:
* ADD (SP plus immediate)
* ADD (SP plus register)
* SUB (SP minus immediate)
* SUB (SP minus register)
* MOV (register)
Backports commit 5520318939fea5d659bf808157cd726cb967b761 from qemu
It has not had users since f83311e476 ("target-m68k: use floatx80
internally", 2017-06-21).
Note that no other bit-width has floatX_trunc_to_int.
Backports commit c953da8f0be5e026d1c9128660736d72294feb3e from qemu
