Fold simple named arrays

[jleben]

If a name refers to a simple array (e.g. one that only copies values from other arrays), replace its references with the array.

This would simplify array reduction as we wouldn't need to be careful with lamda lifting arrays - we could always lift them and this optimization would fold them back if possible.

[jleben]

This is now more critical: recent changes result in more arrays lambda lifted, harming the output code.