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

test/mjsunit/wasm/divrem-trap.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 assertTraps(code, msg) {
   var threwException = true;
@@ skipping 13 matching lines @@
     }
     // Success.
     return;
   }
   throw new MjsUnitAssertionError("Did not throw exception");
 }
 
 
 function makeDivRem(opcode) {
   var kBodySize = 5;
-  var kNameMainOffset = 6 + 11 + kBodySize + 1;
+  var kNameMainOffset = kHeaderSize + 6 + 11 + kBodySize + 1;
 
-  var data = bytes(
+  var data = bytesWithHeader(
     // signatures
     kDeclSignatures, 1,
     2, kAstI32, kAstI32, kAstI32, // (int,int) -> int
     // -- main function
     kDeclFunctions, 1,
     kDeclFunctionName | kDeclFunctionExport,
     0, 0,
     kNameMainOffset, 0, 0, 0,   // name offset
     kBodySize, 0,
     // main body
@@ skipping 41 matching lines @@
 assertEquals( 3, remu(-443, 10));
 
 assertTraps(kTrapRemByZero, "rems(100, 0);");
 assertTraps(kTrapRemByZero, "rems(-1009, 0);");
 
 assertTraps(kTrapRemByZero, "remu(200, 0);");
 assertTraps(kTrapRemByZero, "remu(-2009, 0);");
 
 assertEquals(-2147483648, remu(0x80000000, -1));
 assertEquals(0, rems(0x80000000, -1));