[Issue 23793] std.stdio.openNetwork should be refactored and moved to a different place

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23793

--- Comment #4 from Adam D. Ruppe <destructionator at gmail.com> ---
> The reason is that all the transitive imports are done inside `std.stdio.openNetwork`, and D compiler does not import them, unless it needs to compile `openNetwork` function itself.

That's not true for normal functions, only templates.

> In terms of compatibility, it was working before, now with this function present, I get things like this:

This function was added 13 years ago and barely changed since then, so how long
ago are you looking?

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