ES6 symbols: Implement Symbol intrinsic and basic functionality

src/SConscript

 # Copyright 2012 the V8 project authors. 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
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 308 matching lines @@
 date.js
 regexp.js
 json.js
 liveedit-debugger.js
 mirror-debugger.js
 debug-debugger.js
 '''.split()
 
 
 EXPERIMENTAL_LIBRARY_FILES = '''
+symbol.js
 proxy.js
 collection.js
 '''.split()
 
 
 def Abort(message):
   print message
   sys.exit(1)
 
 
@@ skipping 63 matching lines @@
       snapshot_cc = 'snapshot.cc'
     snapshot_obj = context.ConfigureObject(env, snapshot_cc, CPPPATH=['.'])
   else:
     snapshot_obj = empty_snapshot_obj
   library_objs = [non_snapshot_files, libraries_obj, experimental_libraries_obj, snapshot_obj]
   return (library_objs, d8_objs, [mksnapshot], preparser_objs)
 
 
 (library_objs, d8_objs, mksnapshot, preparser_objs) = ConfigureObjectFiles()
 Return('library_objs d8_objs mksnapshot preparser_objs')