RFR(L) Valhalla support for AArch64 v.05

[Roland Westrelin]

Hi Dmitry,

> I updated the webrev below to lworld_stable. All tests are passed.
>
> Is there any chance to have the changes reviewed and pushed?

I went over the changes quickly and while I can't say I reviewed them I
see no reason not to push them. I also propose we nominate you as
valhalla committer so you can proceed with subsequent pushes
yourself. We can either wait until the CFV is over or I can push them
for you. What do you think?

Roland.