Added to `Int3` ExSwift-like `clamp(…)` & `random(…)`
Added to `Int3` ExSwift-like `clamp(…)` & `random(…)`

* Added new mutating `clamp(_:Range<Int3>)` & `clamp(_ min:Int3, _ max:Int3)` methods, the latter of which does `min()`/`max()`-ing on each component, and the former passes through to the latter.  
	‣ Originally, I wrote this to just use `min()`/`max()` on the whole `Int3` but that was a dumb mistake— it would've used `func <(a:Int3,b:Int3) -> Bool` to determine which is higher, and the `<` is a “true” less-then not a “comparable” less-then— it makes sure all 3 components are less.  _In short, it would've roughly-clamped the `Int3`, giving us at least 1 component that fits the top/bottom bounds and up to 2 components over/under-clamped._
	* Added new non-mutating variants `clamped(_:Range<Int3>) -> Int3` & `clamped(_ min:Int3, _ max:Int3) -> Int3`; the latter creates & clamps an intermediate `value:Int3`; the former hands off to the latter.  
		‣ Went with Swift API Design Guidelines-conformant naming for these instead of matching the ExSwift naming.
* New static `random(min:Int3, max:Int3) -> Int3` method; API and implementation like ExSwift's `Int.random()`.  
	‣ Decided to just implement it outright (using `arc4random_uniform()`) instead of using ExSwift's `Int.random()` because general-purpose libraries that require other libraries are dumb.
capnslipp/IntN,capnslipp/IntN