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

test/mjsunit/wasm/stackwalk.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 --expose-gc --allow-natives-syntax
 
 load("test/mjsunit/wasm/wasm-constants.js");
 
 function makeFFI(func) {
   var kBodySize = 6;
-  var kNameFunOffset = 24 + kBodySize + 1;
+  var kNameFunOffset = kHeaderSize + 24 + kBodySize + 1;
   var kNameMainOffset = kNameFunOffset + 4;
 
   var ffi = new Object();
   ffi.fun = func;
 
-  var data = bytes(
+  var data = bytesWithHeader(
     // signatures
     kDeclSignatures, 1,
     2, kAstI32, kAstF64, kAstF64, // (f64,f64) -> int
     // -- foreign function
     kDeclFunctions, 2,
     kDeclFunctionName | kDeclFunctionImport,
     0, 0,
     kNameFunOffset, 0, 0, 0,    // name offset
     // -- main function
     kDeclFunctionName | kDeclFunctionExport,
@@ skipping 98 matching lines @@
   var gcer = builder(dogc);
   gcer(7, 7);
 
   for (var i = 0; i < 9; i++) {
     gcer(8, 8);
   }
 }
 
 runTest(makeReentrantFFI);
 runTest(makeFFI);