[turbofan] Turn Math.clz32 into an inlinable builtin.

test/mjsunit/asm/math-clz32.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+var stdlib = { Math: Math };
+
+var f = (function Module(stdlib) {
+  "use asm";
+
+  var clz32 = stdlib.Math.clz32;
+
+  function f(a) {
+    a = a >>> 0;
+    return clz32(a)|0;
+  }
+
+  return f;
+})(stdlib);
+
+assertEquals(32, f(0));
+assertEquals(32, f(NaN));
+assertEquals(32, f(undefined));
+for (var i = 0; i < 32; ++i) {
+  assertEquals(i, f((-1) >>> i));
+}
+for (var i = -2147483648; i < 2147483648; i += 3999773) {
+  assertEquals(%MathClz32(i), f(i));
+  assertEquals(%_MathClz32(i), f(i));
+}