Unicode operators

[Walter Bright]

Bill Baxter wrote:
> I think it was Ocaml or something allows you to declare new infix
> operators with precedence based on other operators.  So with that you
> can kind of create a "subclass" of the multiply operator, that has
> similar precedence.  That seems elegant to me.

That goes against a design principle of D, that it must be parsable 
without semantic analysis.