Index: abi/include/_bits/NULL.h
===================================================================
--- abi/include/_bits/NULL.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
+++ abi/include/_bits/NULL.h	(revision c9f3e7e90bf5ef1a7d8f76f8717c35a796152375)
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2017 CZ.NIC, z.s.p.o.
+ * 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 with the distribution.
+ * - The name of the author may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* Authors:
+ *	Jiří Zárevúcky (jzr) <zarevucky.jiri@gmail.com>
+ */
+
+/** @addtogroup bits
+ * @{
+ */
+/** @file
+ * Definition of constant NULL.
+ *
+ * This definition is designed to work in both C and C++, and use
+ * the special constant `nullptr` in C++11 and above.
+ * Including this file is preferrable to defining the constant separately.
+ */
+
+#ifndef _BITS_NULL_H_
+#define _BITS_NULL_H_
+
+#ifndef NULL
+
+#if __cplusplus >= 201103L
+#define NULL  nullptr
+#elif defined(__cplusplus)
+#define NULL  0L
+#else
+#define NULL  ((void *) 0)
+#endif
+
+#endif
+
+#endif
+
+/** @}
+ */