[wasm] Add a magic word and a version number to the binary.

test/mjsunit/wasm/ffi-error.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: --expose-wasm
 
 load("test/mjsunit/wasm/wasm-constants.js");
 
 function testCallFFI(ffi) {
   var kBodySize = 6;
-  var kNameAddOffset = 28 + kBodySize + 1;
+  var kNameAddOffset = kHeaderSize + 28 + kBodySize + 1;
   var kNameMainOffset = kNameAddOffset + 4;
 
-  var data = bytes(
+  var data = bytesWithHeader(
     kDeclMemory,
     12, 12, 1,                  // memory
     // -- signatures
     kDeclSignatures, 1,
     2, kAstI32, kAstF64, kAstF64, // (f64,f64)->int
     // -- foreign function
     kDeclFunctions, 2,
     kDeclFunctionName | kDeclFunctionImport,
     0, 0,                       // signature index
     kNameAddOffset, 0, 0, 0,    // name offset
@@ skipping 45 matching lines @@
   testCallFFI(ffi);
 });
 
 
 // "fun" should be a JS function.
 assertThrows(function() {
   var ffi = new Object();
   ffi.fun = 0;
   testCallFFI(ffi);
 });