For the following:

```
def f(*a); a end
p f(*a, kw: 3)
```

`setup_parameters_complex` pushes `{kw: 3}` onto `a`.  This worked fine
back when `concatarray true` was used and `a` was already a copy. It
does not work correctly with the optimization to switch to
`concatarray false`.  This duplicates the array on the callee side
in such a case.

This affects cases when passing a regular splat and a keyword splat
(or literal keywords) in a method call, where the method does not
accept keywords.

This allocation could probably be avoided, but doing so would
make `setup_parameters_complex` more complicated.