collection of small fixes from running runtime tests with -Xcomp

[Roland Westrelin]

> Is C2 code relying on the ValueFactory_attribute used by vnew?
> Vnew and this attribute are supposed to be removed in favor of the
> vdefault/vwithfield solution to create values. If this is likely to cause
> issues to C2, it’s time to speak up.

I don't think we have a problem with vnew and the ValueFactory_attribute
going away. We'll just have to adjust the code.

Roland.