[builtins] Introduce proper Float64Tan operator.

test/mjsunit/double-intrinsics.js

 // Copyright 2014 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
 
 function assertDoubleBits(hi, lo, x) {
   hi = hi | 0;
   lo = lo | 0;
-  assertEquals(x, %_ConstructDouble(hi, lo));
+  assertEquals(x, %ConstructDouble(hi, lo));
   assertEquals(hi, %_DoubleHi(x));
   assertEquals(lo, %_DoubleLo(x));
-  assertEquals(x, %_ConstructDouble(%_DoubleHi(x), %_DoubleLo(x)));
+  assertEquals(x, %ConstructDouble(%_DoubleHi(x), %_DoubleLo(x)));
 }
 
 
 var tests = [0x7ff00000, 0x00000000, Infinity,
              0xfff00000, 0x00000000, -Infinity,
              0x80000000, 0x00000000, -0,
              0x400921fb, 0x54442d18, Math.PI,
              0xc00921fb, 0x54442d18, -Math.PI,
              0x4005bf0a, 0x8b145769, Math.E,
              0xc005bf0a, 0x8b145769, -Math.E,
              0xbfe80000, 0x00000000, -0.75];
 
 
 for (var i = 0; i < tests.length; i += 3) {
   assertDoubleBits(tests[i], tests[i + 1], tests[i + 2]);
 }
 
 %OptimizeFunctionOnNextCall(assertDoubleBits);
 
 for (var i = 0; i < tests.length; i += 3) {
   assertDoubleBits(tests[i], tests[i + 1], tests[i + 2]);
   assertOptimized(assertDoubleBits);
 }