Evaluation order issues

[quasilyte]

The gc and gccgo evaluate some expressions in different ways.
It's not absolutely clear where is the boundary between unspecified and misinterpreted spec
description of evaluation order.

This issue is to track evaluation order related tickets.
It's very desirable not to another kind of evaluation order variant,
so it can be great to add evaluation order tests that check output
against gc and/or gccgo.

(Not using real links to avoid github cross-references)
go#23188
go#24448
go#23017
go#25609
go#15620