Update re2

third_party/re2/util/flags.h

 // Copyright 2009 The RE2 Authors.  All Rights Reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // Simplified version of Google's command line flags.
 // Does not support parsing the command line.
 // If you want to do that, see
-// http://code.google.com/p/google-gflags
+// https://gflags.github.io/gflags/
 
 #ifndef RE2_UTIL_FLAGS_H__
 #define RE2_UTIL_FLAGS_H__
 
 #define DEFINE_flag(type, name, deflt, desc) \
         namespace re2 { type FLAGS_##name = deflt; }
 
 #define DECLARE_flag(type, name) \
         namespace re2 { extern type FLAGS_##name; }
 
 #define DEFINE_bool(name, deflt, desc) DEFINE_flag(bool, name, deflt, desc)
 #define DEFINE_int32(name, deflt, desc) DEFINE_flag(int32, name, deflt, desc)
 #define DEFINE_string(name, deflt, desc) DEFINE_flag(string, name, deflt, desc)
 
 #define DECLARE_bool(name) DECLARE_flag(bool, name)
 #define DECLARE_int32(name) DECLARE_flag(int32, name)
 #define DECLARE_string(name) DECLARE_flag(string, name)
 
 #endif  // RE2_UTIL_FLAGS_H__