Fix instable array during in-place modification in uksort

[iluuu1994]

The array isn't just observable if the array has RCn, but also if it is inside a reference that is RCn. By-ref parameters are always RCn and as such always observable.

Fixes GH-13279

[iluuu1994]

By-ref parameters are always RCn and as such always observable.

Actually, this is wrong. CVs pass the reference without increasing the refcount. So there might be some benefit to this after all. I'll check this after lunch.

[nielsdos]

Thank you Ilija!
I'm fine with this as-is to be honest.
How commonly, after correctly fixing this, would the optimization be used in real-world code? I expect very few times when adding additional restrictions. So therefore, I prefer simpler code over potentially hard-to-understand code when the benefit is negligible. :-)

[iluuu1994]

I agree. My last comment was also incorrect. I was thinking of CV opcode args with their refcount not being increased, rather than function arguments. So checking for RC1 will be useless.

[nielsdos]

Let's go with this

[bukka]

I guess this should go to ext/standard/tests/array

[iluuu1994]

Done. TBH the separation of these tests is often quite arbitrary. I usually just throw stuff in Zend.