[expr.call] [dcl.fct] Move return type requiremens

[languagelawyer]

An array element type is constrained by [dcl.array]/4:

U is called the array element type; this type shall not be a placeholder type ([dcl.spec.auto]), a reference type, a function type, an array of unknown bound, or cv void.

[languagelawyer]

It is funny that this removes prohibition on array return type and it was approved as an editorial change

patch changed

[tkoeppe]

@jensmaurer: do you think this is ready to go? I would perhaps like a more detailed commit message explaining why the big deletion is warranted.

[jensmaurer]

@tkoeppe: I think this is ready to go. The "array of function" prohibition is in [dcl.array] p4. The rest is just fluff / wordiness.

I'm merging it and fixing the commit description.

[tkoeppe]

Thanks, @jensmaurer!