[swift-evolution] [pitch] remove global sqrt<T: FloatingPoint>

[Stephen Canon]

Post SE-0067 FloatingPoint provides the usual global operators, as well as a single global function:

	func sqrt<T: FloatingPoint>(_: T) -> T

It seems out of place and lonely, and it would be nice if we can keep the default members of the global namespace to a minimum.

I’d like to suggest removing this global from FloatingPoint while keeping the existing global functions for concrete types in the Darwin.C module.  The square root operation would still be available for all FloatingPoint types as `.squareRoot()`.

I would also plan to provide this and other math.h-ish globals in a future (post swift 3) Math module.

– Steve