LLVM 10 release notes for SystemZ

[Hans Wennborg via llvm-commits]

On Mon, Feb 10, 2020 at 7:18 PM Ulrich Weigand via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> I just noticed that I forgot to add LLVM 10 release notes for the SystemZ target. Here's a patch to the branch:
> (See attached file: llvm10-system-relnotes.diff)
>
> If it's not too late yet, could you please add this? (Or if you prefer me to commit it myself, let me know.)

Looks good, thanks! Go ahead and push directly to the branch, or let
me know and I can do it for you.

Thanks,
Hans