[benchmark] Extract setup from ArrayInClass

ArrayInClass had setup overhead of 88 μs (17%).

Author: palimondo

benchmark/single-source/ArrayInClass.swift

@@ -14,7 +14,11 @@ import TestsUtils
 public let ArrayInClass = BenchmarkInfo(
   name: "ArrayInClass",
   runFunction: run_ArrayInClass,
-  tags: [.validation, .api, .Array])
+  tags: [.validation, .api, .Array],
+  setUpFunction: { ac = ArrayContainer() },
+  tearDownFunction: { ac = nil })
+
+var ac: ArrayContainer!
 
 class ArrayContainer {
   final var arr : [Int]
@@ -32,13 +36,8 @@ class ArrayContainer {
   }
 }
 
-@inline(never)
-func getArrayContainer() -> ArrayContainer {
-  return ArrayContainer()
-}
-
 @inline(never)
 public func run_ArrayInClass(_ N: Int) {
-  let a = getArrayContainer()
+  let a = ac!
   a.runLoop(N)
 }