float equality

[Walter Bright]

spir wrote:
> "Naturally" non-representable numbers (irrationals), or results of 
> "naturally" approximate operations (like trig), are not an issue because 
> they are expected to yield inaccuracy.

Huh, I regularly run into people who are befuddled by the trig functions not 
conforming to the usual trig identity equations.

Worse, I also regularly run into crappy sloppy implementations of the 
transcendental functions that lose excessive bits of accuracy (I'm looking at 
you, FreeBSD and OSX). Don has been moving std.math to using our own 
implementations because of this, avoiding dependency on crappy C libraries 
written by people who do not understand or care about FP math.