Revert "Revert "Update aosp/master libcxx rebase to r263688""

This reverts commit 1d4a1edbc7.

Change-Id: I2909937fe582f2c5552bc86e7f4d2d5cff0de0aa

include/stdbool.h

@@ -0,0 +1,39 @@
+// -*- C++ -*-
+//===--------------------------- stdbool.h --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_STDBOOL_H
+#define _LIBCPP_STDBOOL_H
+
+
+/*
+    stdbool.h synopsis
+
+Macros:
+
+    __bool_true_false_are_defined
+
+*/
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#include_next <stdbool.h>
+
+#ifdef __cplusplus
+#undef bool
+#undef true
+#undef false
+#undef __bool_true_false_are_defined
+#define __bool_true_false_are_defined 1
+#endif
+
+#endif  // _LIBCPP_STDBOOL_H