Mark DispatchTimeInterval Equatable

We can mark `DispatchTimeInterval` as equatable because it already
implements the equality check operator `==`.

Doing this will allow DispatchTimeInterval to be used with a wide range
of library functions which are defined to operate on Equatable objects.
For example this is useful in tests when you might which to use `XCTAssertEqual`.

Author: rnro

src/swift/Time.swift

@@ -165,7 +165,7 @@ private func toInt64Clamped(_ value: Double) -> Int64 {
 /// 	let t1 = DispatchTimeInterval.seconds(Int.max)
 ///		let t2 = DispatchTimeInterval.milliseconds(Int.max)
 ///		let result = t1 == t2   // true
-public enum DispatchTimeInterval {
+public enum DispatchTimeInterval: Equatable {
 	case seconds(Int)
 	case milliseconds(Int)
 	case microseconds(Int)