Fix Phobos dependencies on autodecoding

[jmh530]

On Tuesday, 13 August 2019 at 16:18:03 UTC, H. S. Teoh wrote:
> [snip]
>
> Because it *appears* to be right, but it's actually wrong. For 
> example:
>
> 	import std.range : retro;
> 	import std.stdio;
>
> 	void main() {
> 		writeln("привет".retro);
> 		writeln("приве́т".retro);
> 	}
>
> Expected output:
> 	тевирп
> 	те́вирп
>
> Actual output:
> 	тевирп
> 	т́евирп
>

Huh, those two look the same.