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

test/mjsunit/wasm/instantiate-run-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 = 97;
 
 var kBodySize = 2;
-var kNameOffset = 15 + kBodySize + 1;
+var kNameOffset = kHeaderSize + 15 + kBodySize + 1;
 
-var data = bytes(
+var data = bytesWithHeader(
   // -- signatures
   kDeclSignatures, 1,
   0, kAstI32,                 // signature: void -> int
   // -- main function
   kDeclFunctions, 1,
   kDeclFunctionName | kDeclFunctionExport,
   0, 0,                       // signature index
   kNameOffset, 0, 0, 0,       // name offset
   kBodySize, 0,               // body size
   // -- body
   kExprI8Const,               // --
   kReturnValue,               // --
   kDeclEnd,
   'm', 'a', 'i', 'n', 0       // name
 );
 
 assertEquals(kReturnValue, _WASMEXP_.instantiateModule(data).main());