Without this change, in bleeding-edge fileutils Autoconf complains
that gl_SOCKETLIB etc. are AC_REQUIREd after being invoked.
* modules/socketlib (configure.ac): AC_REQUIRE gl_SOCKETLIB.
* modules/sockets (configure.ac): AC_REQUIRE gl_SOCKETS.
* modules/sys_socket (configure.ac): AC_REQUIRE gl_HEADER_SYS_SOCKET.

* lib/msvc-nothrow.h: New file.
* lib/msvc-nothrow.c: New file.
* m4/msvc-nothrow.m4: New file.
* modules/msvc-nothrow: New file.
* lib/dup2.c: Include msvc-nothrow.h.
(rpl_dup2): No need to protect _get_osfhandle call here.
* lib/accept4.c: Include msvc-nothrow.h.
* lib/error.c: Likewise.
* lib/fcntl.c: Likewise.
* lib/lseek.c: Likewise.
* lib/nonblocking.c: Likewise.
* lib/poll.c: Likewise.
* lib/read.c: Likewise.
* lib/select.c: Likewise.
* lib/sockets.h: Likewise.
* lib/sockets.c: Likewise.
* lib/stdio-read.c: Likewise.
* lib/stdio-write.c: Likewise.
* lib/write.c: Likewise.
* lib/w32sock.h: Likewise.
* lib/w32spawn.h: Likewise.
* lib/flock.c: Include msvc-nothrow.h instead of <io.h>.
* lib/fsync.c: Likewise.
* lib/isapipe.c: Likewise.
* modules/dup2 (Depends-on): Add msvc-nothrow.
* modules/accept4 (Depends-on): Likewise.
* modules/error (Depends-on): Likewise.
* modules/fcntl (Depends-on): Likewise.
* modules/lseek (Depends-on): Likewise.
* modules/nonblocking (Depends-on): Likewise.
* modules/poll (Depends-on): Likewise.
* modules/read (Depends-on): Likewise.
* modules/select (Depends-on): Likewise.
* modules/sockets (Depends-on): Likewise.
* modules/sigpipe (Depends-on): Likewise.
* modules/write (Depends-on): Likewise.
* modules/accept (Depends-on): Likewise.
* modules/bind (Depends-on): Likewise.
* modules/connect (Depends-on): Likewise.
* modules/gethostname (Depends-on): Likewise.
* modules/getpeername (Depends-on): Likewise.
* modules/getsockname (Depends-on): Likewise.
* modules/getsockopt (Depends-on): Likewise.
* modules/ioctl (Depends-on): Likewise.
* modules/listen (Depends-on): Likewise.
* modules/recv (Depends-on): Likewise.
* modules/recvfrom (Depends-on): Likewise.
* modules/send (Depends-on): Likewise.
* modules/sendto (Depends-on): Likewise.
* modules/setsockopt (Depends-on): Likewise.
* modules/shutdown (Depends-on): Likewise.
* modules/socket (Depends-on): Likewise.
* modules/execute (Depends-on): Likewise.
* modules/spawn-pipe (Depends-on): Likewise.
* modules/flock (Depends-on): Likewise.
* modules/fsync (Depends-on): Likewise.
* modules/isapipe (Depends-on): Likewise.
* tests/test-cloexec.c: Include msvc-nothrow.h.
* tests/test-dup-safer.c: Likewise.
* tests/test-dup2.c: Likewise.
* tests/test-dup3.c: Likewise.
* tests/test-fcntl.c: Likewise.
* tests/test-pipe.c: Likewise.
* tests/test-pipe2.c: Likewise.
* modules/cloexec-tests (Depends-on): Add msvc-nothrow.
* modules/unistd-safer-tests (Depends-on): Likewise.
* modules/dup2-tests (Depends-on): Likewise.
* modules/dup3-tests (Depends-on): Likewise.
* modules/fcntl-tests (Depends-on): Likewise.
* modules/pipe-posix-tests (Depends-on): Likewise.
* modules/pipe2-tests (Depends-on): Likewise.

* lib/fd-hook.h: Renamed from lib/close-hook.h.
(gl_close_fn, gl_ioctl_fn): New types.
(struct fd_hook): Renamed from struct close_hook. Change type of
private_close_fn field. Add private_ioctl_fn field.
(close_hook_fn): Add parameter for primary close method.
(execute_close_hooks, execute_all_close_hooks): Likewise.
(ioctl_hook_fn): New type.
(execute_ioctl_hooks, execute_all_ioctl_hooks): New declarations.
(register_fd_hook): Renamed from register_close_hook. Add ioctl_hook
argument.
(unregister_fd_hook): Renamed from unregister_close_hook.
* lib/fd-hook.c: Renamed from lib/close-hook.c.
Don't include <unistd.h>.
(close): Remove undef.
(anchor): Update.
(execute_close_hooks): Add argument for primary close method.
(execute_all_close_hooks): Likewise.
(execute_ioctl_hooks, execute_all_ioctl_hooks): New functions.
(register_fd_hook): Renamed from register_close_hook. Add ioctl_hook
argument. Allow each argument to be NULL.
(unregister_fd_hook): Renamed from unregister_close_hook.
* lib/close.c (rpl_close): Pass 'close' function pointer to
execute_all_close_hooks.
* lib/ioctl.c: Include <errno.h>, fd-hook.h.
(primary_ioctl): New function.
(ioctl): Don't call ioctlsocket here. Instead, call
execute_all_ioctl_hooks.
* lib/sockets.c (close_fd_maybe_socket): Add argument for primary
close method.
(ioctl_fd_maybe_socket): New function, with code from lib/ioctl.c.
(fd_sockets_hook): Renamed from close_sockets_hook.
(gl_sockets_startup, gl_sockets_cleanup): Update.
* modules/fd-hook: Renamed from modules/close-hook. Update.
* modules/close (Depends-on): Add fd-hook, remove close-hook.
* modules/sockets (Depends-on): Likewise.
* modules/ioctl (Depends-on): Add fd-hook.
* tests/test-nonblocking.c (main): Use GNULIB_TEST_SOCKET, not
GNULIB_SOCKET.

* modules/socketlib: New file.
* m4/socketlib.m4: New file, extracted from m4/sockets.m4.
* m4/sockets.m4 (gl_SOCKETS): Require gl_SOCKETLIB.
* modules/sockets (Depends-on): Add socketlib.
Suggested by Sam Steingold <sds@gnu.org>.