[PATCH] RISC-V : Support bitmanip-0.93 ZBA/ZBB/ZBC instructions

[Kito Cheng]

> This looks good to me.  I think this is OK to install.
>
> Do we want a -menable-experimental-extensions option to control this since
> it is frozen but not yet accepted?  Or do we want to accept it as is?  We
> can worry about this after the patch goes in since it doesn't really matter
> until the next binutils release.

I would prefer to keep those behind -menable-experimental-extensions,
they are frozen, but I think it's still not clear enough on RVB spec...

And this could be a separate patch, just done before the next release
is fine to me.