[turbofan] Fix truncation/representation sloppiness wrt. bool/bit.

test/mjsunit/compiler/regress-3812.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.
 
 var stdlib = this;
 var buffer = new ArrayBuffer(64 * 1024);
 var foreign = {}
 
 var foo = (function Module(stdlib, foreign, heap) {
   "use asm";
   function foo(i) {
-    return !(i ? 1 : false);
+    var x = i ? (i&1) : true;
+    if (x) return x;
+    return false;
   }
   return {foo:foo};
 })(stdlib, foreign, buffer).foo;
 
-assertFalse(foo(1));
-assertTrue(foo(0));
+assertEquals(1, foo(1));