std.string.join & co. do a character-by-character copy because hasLength!string is false

[Vladimir Panteleev]

Why hasLength!string is false:  
https://github.com/D-Programming-Language/phobos/blob/96941d5384a5fee302df/std/range.d#L767

Would it make sense to introduce a hasOpaqueLength oslt. to fix this?
--
Best regards,
 Vladimir                            mailto:vladi...@thecybershadow.net