Fix warnings in veccore that arise when compiling ROOT

[guitargeek]

When including Vc.h, ROOT Math disables several compiler diagnostics to avoid warnings in the CI and nightlies:
https://github.com/root-project/root/blob/0fd27057b7b25e777ea642dfcc216ab27a6ece0d/math/mathcore/inc/Math/Types.h

It would be good if any warnings can be avoided in upstream veccore, such that we don't need this hack in ROOT.

[amadio]

I think I agree with Lorenzo on this, the warnings should probably be fixed directly in Vc, since that's where they come from. We have taken over maintenance of it some time ago, so we can just fix these warnings and make a new patch release if needed. @Axel-Naumann has write permission to make the actual release, and @bernhardmgruber and I can merge pull requests with fixes. I think VecCore as the middleman is not really the right place to apply a fix.

[guitargeek]

Oh sorry, I didn't know Vc and veccore were not the same thing! Should I open this issue also for Vc then?

[amadio]

Yes, please. Thanks! The repo is https://github.com/VcDevel/Vc