Dump special floating point operators

[Don]

Walter Bright wrote:
> !<>=
> <>
> <>=
> !<=
> !<
> !>=
> !>
> !>=
> 
> http://www.digitalmars.com/d/2.0/expression.html#RelExpression
> 
> While I like them a lot, it's time for them to go:
> 
> 1. It's hard to remember which one does what
> 2. They've failed to catch on
> 3. No operator overloading for them
> 4. They are only rarely needed; a special operator is not justified

I think I've used them more than anyone else, and I agree. What I've 
noticed is that you _always_ want to treat NaNs as a special case. In 
asm, you can have a 3-way branch: eg,

  cmp a, b;
  jp L_nan;
  jl L_less;
Lgreater_eq: // a >= b

L_less:  // a < b

L_nan: // a or b is NaN.

But the NCEG operators don't let you do that. They only allow you to 
chose which way NaNs should go. In almost all cases, you can replace 
a!>b with !(a<=b), so the cases where they are beneficial are very, very 
limited.
Currently one use is in CTFE:
isNaN(x) doesn't work in CTFE at the moment, whereas x<>=0 does. But of 
course isNaN should work in CTFE.