Higher level built-in strings

[Walter Bright]

Steven Schveighoffer wrote:
> The omission of dchar is on purpose.  Phobos has characterized string as 
> a bidirectional range of dchars.  For every range where I do:
> 
> foreach(e; range)
> 
> e is of the type of the range.  Except for char and wchar.  This 
> schizophrenia of type induction is very bad for D, and it's a good 
> argument of why strings should not simply be arrays.

For many algorithms on strings, iterating by char is preferred over dchar, even 
for multibyte strings.