[proxies] Remove "fix" functionality, add (still unused) target property.

test/mjsunit/harmony/regress/regress-405844.js

 // Copyright 2014 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: --harmony-proxies --harmony-object-observe
 
-var proxy = Proxy.create({ fix: function() { return {}; } });
-Object.preventExtensions(proxy);
-Object.observe(proxy, function(){});
+// TODO(neis): These tests are temporarily commented out because of ongoing
+// changes to the implementation of proxies.
 
-var functionProxy = Proxy.createFunction({ fix: function() { return {}; } }, function(){});
-Object.preventExtensions(functionProxy);
-Object.observe(functionProxy, function(){});
+//var proxy = Proxy.create({ fix: function() { return {}; } });
+//Object.preventExtensions(proxy);
+//Object.observe(proxy, function(){});
+//
+//var functionProxy = Proxy.createFunction({ fix: function() { return {}; } }, function(){});
+//Object.preventExtensions(functionProxy);
+//Object.observe(functionProxy, function(){});