disabling unary "-" for unsigned types

[Justin Johansson]

Andrei Alexandrescu wrote:
> ulong x0;
> static assert(!__traits(compiles, -x0));
> uint x1;
> static assert(!__traits(compiles, -x1));
> ushort x2;
> static assert(!__traits(compiles, -x2));
> ubyte x3;
> static assert(!__traits(compiles, -x3));
> 
> Sounds good?
> 
> Andrei

Sounds excellent.  Who would have thought of that?

Cheers
Justin Johansson