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

test/mjsunit/wasm/instantiate-module-basic.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");
 
 var kReturnValue = 117;
 
 var kBodySize = 2;
-var kNameOffset = 19 + kBodySize + 1;
+var kNameOffset = kHeaderSize + 19 + kBodySize + 1;
 
-var data = bytes(
+var data = bytesWithHeader(
   // -- memory
   kDeclMemory,
   10, 10, 1,
   // -- signatures
   kDeclSignatures, 1,
   0, kAstI32,                 // signature: void -> int
   // -- main function
   kDeclFunctions, 1,
   kDeclFunctionName | kDeclFunctionExport,
   0, 0,                       // signature index
@@ skipping 28 matching lines @@
 
 assertEquals(1024, module.memory.byteLength);
 
 // Check the properties of the main function.
 assertFalse(module.main === undefined);
 assertFalse(module.main === null);
 assertFalse(module.main === 0);
 assertEquals("function", typeof module.main);
 
 assertEquals(kReturnValue, module.main());