Absolutely horrible default string hashing

[Sean Kelly]

Andrei Alexandrescu wrote:
> 
> I have exchanged email with Paul Hsieh about using his hash function in 
> Phobos (azillionmonkeys.com) and he said his license is very permissive. 
> I seem to recall I have introduced his hash function, with credit, in 
> Phobos' old runtime but I am not sure whether Sean took that over. I 
> suggest we do that in druntime for string, be they mutable or not.

Unfortunately, that request is languishing in the "oops, I forgot" 
portion of my to-do list.