Use C++11 / gnu++11, not 0x

.ycm_extra_conf.py

 # 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.
 
 # Autocompletion config for YouCompleteMe in V8.
 #
 # USAGE:
 #
 #   1. Install YCM [https://github.com/Valloric/YouCompleteMe]
 #          (Googlers should check out [go/ycm])
@@ skipping 24 matching lines @@
 
 import os
 import os.path
 import subprocess
 import sys
 
 
 # Flags from YCM's default config.
 flags = [
 '-DUSE_CLANG_COMPLETER',
-'-std=gnu++0x',
+'-std=gnu++11',
 '-x',
 'c++',
 ]
 
 
 def PathExists(*args):
   return os.path.exists(os.path.join(*args))
 
 
 def FindV8SrcFromFilename(filename):
@@ skipping 128 matching lines @@
       'flags': (List of Strings) Command line flags.
       'do_cache': (Boolean) True if the result should be cached.
   """
   v8_root = FindV8SrcFromFilename(filename)
   v8_flags = GetClangCommandFromNinjaForFilename(v8_root, filename)
   final_flags = flags + v8_flags
   return {
     'flags': final_flags,
     'do_cache': True
   }