Use Gnulib's `nproc'.

This updates Gnulib to v0.0-4496-g6491120.

* m4/gnulib-cache.m4: Add `nproc'.

lib/close-hook.h

@@ -0,0 +1,72 @@
+/* Hook for making the close() function extensible.
+   Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+
+   This program 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 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+
+#ifndef CLOSE_HOOK_H
+#define CLOSE_HOOK_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/* Currently, this entire code is only needed for the handling of sockets
+   on native Windows platforms.  */
+#if WINDOWS_SOCKETS
+
+
+/* An element of the list of close hooks.
+   The fields of this structure are considered private.  */
+struct close_hook
+{
+  /* Doubly linked list.  */
+  struct close_hook *private_next;
+  struct close_hook *private_prev;
+  /* Function that treats the types of FD that it knows about and calls
+     execute_close_hooks (FD, REMAINING_LIST) as a fallback.  */
+  int (*private_fn) (int fd, const struct close_hook *remaining_list);
+};
+
+/* This type of function closes FD, applying special knowledge for the FD
+   types it knows about, and calls execute_close_hooks (FD, REMAINING_LIST)
+   for the other FD types.  */
+typedef int (*close_hook_fn) (int fd, const struct close_hook *remaining_list);
+
+/* Execute the close hooks in REMAINING_LIST.
+   Return 0 or -1, like close() would do.  */
+extern int execute_close_hooks (int fd, const struct close_hook *remaining_list);
+
+/* Execute all close hooks.
+   Return 0 or -1, like close() would do.  */
+extern int execute_all_close_hooks (int fd);
+
+/* Add a function to the list of close hooks.
+   The LINK variable points to a piece of memory which is guaranteed to be
+   accessible until the corresponding call to unregister_close_hook.  */
+extern void register_close_hook (close_hook_fn hook, struct close_hook *link);
+
+/* Removes a function from the list of close hooks.  */
+extern void unregister_close_hook (struct close_hook *link);
+
+
+#endif
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CLOSE_HOOK_H */