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

test/mjsunit/wasm/unreachable.js

Index: test/mjsunit/wasm/unreachable.js
diff --git a/test/mjsunit/wasm/unreachable.js b/test/mjsunit/wasm/unreachable.js
index 10eea2323065df9d204762a50552ae02416b6cc1..ff8759b84c4df40178ed130693f94da2f5ff3f03 100644
--- a/test/mjsunit/wasm/unreachable.js
+++ b/test/mjsunit/wasm/unreachable.js
@@ -10,12 +10,12 @@ var module = (function () {
   var kFuncWithBody = 9;
   var kFuncImported = 7;
   var kBodySize1 = 1;
-  var kMainOffset = 6 + kFuncWithBody + kBodySize1 + 1;
+  var kMainOffset = kHeaderSize + 6 + kFuncWithBody + kBodySize1 + 1;
 
   var ffi = new Object();
   ffi.add = (function(a, b) { return a + b | 0; });
 
-  return _WASMEXP_.instantiateModule(bytes(
+  return _WASMEXP_.instantiateModule(bytesWithHeader(
     // -- signatures
     kDeclSignatures, 1,
     0, kAstStmt, // void -> void