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

[Walter Bright]

On 11/4/2021 7:41 PM, Mathias LANG wrote:
> If you want to fix it, just deprecate the special case and tell people to use 
> `foreach (dchar d; someString.byUTF!(dchar, No.useReplacementDchar))` and voilà.
> And if they don't want it to throw, it's shorter:
> `foreach (dchar d; someString.byUTF!dchar)` (or `byDChar`).

People will always gravitate towards the smaller, simpler syntax. Like [] 
instead of std::vector<>.