Use appropriate API for given OSX/macOS level

Author: Joshua Liebowitz

Tests/ReactiveSwiftTests/SignalProducerSpec.swift

@@ -794,7 +794,13 @@ class SignalProducerSpec: QuickSpec {
 			}
 
 			it("shouldn't overflow on a real scheduler") {
-				let scheduler = QueueScheduler()
+				let scheduler: QueueScheduler
+				if #available(OSX 10.10, *) {
+					scheduler = QueueScheduler(qos: .default, name: "\(#file):\(#line)")
+				} else {
+					scheduler = QueueScheduler(queue: DispatchQueue(label: "\(#file):\(#line)"))
+				}
+
 				let producer = timer(interval: 3, on: scheduler)
 				producer
 					.start()