[Amendment] SE-0368: StaticBigInt

[tera]

@bbrk24

Even if it only affected Double, it could still be source-breaking in some edge cases:

Source-breaking - yes. Worth "fixing" - I'd also say yes.

let a: Double = -0
print(a.sign) // plus

let b: Double = -0.0
print(b.sign) // minus

let c: Double = -(0)
print(c.sign) // minus

let d: Double = -(0.0)
print(d.sign) // minus

let O: Double = 0

let e: Double = -O
print(e.sign) // minus

let f: Double = -(O)
print(f.sign) // minus