collection of small fixes from running runtime tests with -Xcomp

[Tobias Hartmann]

On 15.03.2017 09:21, Roland Westrelin wrote:
> Anyway, we at least need a workaround for this. Are you ok with the one
> I used?

Sure, fine with me.

> Why not set TieredCompilation to false in arguments.cpp once for all?

Right, that's even better.

Thanks,
Tobias