Fix: Element-wise `min`/`max(Int3,Int3)`, like `simd.min`/`max()`
Fix: Element-wise `min`/`max(Int3,Int3)`, like `simd.min`/`max()`

Moved from calling `Swift.min`/`.max(…)` thrice for the method `clamp(…)` to new implementations of `Int3` `min(…)` & `max(…)` global free functions.

* New `min(_:Int3,_:Int3) -> Int3` & `min(_:Int3,_:Int3,_:Int3,_:Int3…) -> Int3` functions compute the minimum (per-axis) for 2 `Int3`s or ≥3 `Int3`s.  
	‣ Both forms derived from Swift's own `Swift.min(…)` source code— the 2-arg form uses `<` checks, and the ≥3-arg form uses `min(…)`s for the first 3 args and a loop for the `rest`.
* New `max(_:Int3,_:Int3) -> Int3` & `max(_:Int3,_:Int3,_:Int3,_:Int3…) -> Int3` functions compute the maximum (per-axis) for 2 `Int3`s or ≥3 `Int3`s.  
	‣ Likewise derived from Swift's own `Swift.max(…)` source code.
* Updated `clamp(…)` & `clamped(…)` methods to use new `min(…)` & `max(…)` functions.
capnslipp/IntN,capnslipp/IntN