[master] 55995ab0f Renovate libvarnisapi signal handling.

[Dridi Boukelmoune]

>     The old VUT_Signal()/VUT_Signaled() API is retained and should be
>     deprecated in a future version.

Should we have a dummy vut akin to vmod-debug to extend our coverage
of libvarnishapi?

I haven't reviewed this yet, but that would allow test coverage of
this kind of changes and help a lot when we consider bringing the
improvement to the 6.0 branch. (And also make sure we don't break
the existing feature while it's still present and then deprecated.)

My intuition tells me that this one will be a no-no and may even
require an soname bump.

Dridi