Add wtf_unittests target that links unit tests outside DLL

Source/modules/modules.gyp

 #
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
     'modules.gypi',
   ],
   'targets': [{
     'target_name': 'modules',
     'type': 'static_library',
     'dependencies': [
       '<(DEPTH)/third_party/zlib/zlib.gyp:zlib',
       '../config.gyp:config',
       '../core/core.gyp/core.gyp:webcore',
     ],
+    'defines': [
+      'WEBKIT_IMPLEMENTATION=1',
+    ],
     'sources': [
       '<@(modules_files)',
     ],
     # Disable c4267 warnings until we fix size_t to int truncations.
     'msvs_disabled_warnings': [ 4267, 4334, ]
   }],
 }