dmd foreach loops throw exceptions on invalid UTF sequences, use replacementDchar instead

[Walter Bright]

On 11/4/2021 12:55 AM, Elronnd wrote:
> Part of the problem, as mentioned, is that this throws away information, because 
> text may legitimately contain replacement characters.  (And this makes the 
> 'check if replacement char and throw yourself' approach a non-starter).  But 
> there are lossless encodings.  I think if we are really going to go this route, 
> we should use something like raku's utf8-c8 
> (https://docs.raku.org/language/unicode#UTF8-C8).

There's only one replacement character, and this use is officially what it is 
for. If you're using it for other porpoises, you've got a whale of a problem.