resolv: Deprecate the "inet6" option and RES_USE_INET6 [BZ #19582]

resolv/resolv-internal.h

@@ -0,0 +1,35 @@
+/* libresolv interfaces for internal use across glibc.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _RESOLV_INTERNAL_H
+#define _RESOLV_INTERNAL_H 1
+
+#include <resolv.h>
+#include <stdbool.h>
+
+/* Internal version of RES_USE_INET6 which does not trigger a
+   deprecation warning.  */
+#define DEPRECATED_RES_USE_INET6 0x00002000
+
+static inline bool
+res_use_inet6 (void)
+{
+  return _res.options & DEPRECATED_RES_USE_INET6;
+}
+
+#endif  /* _RESOLV_INTERNAL_H */