Assume POSIX 1003.1-1988 or later for fcntl.h.

Assume POSIX 1003.1-1988 or later for fcntl.h.

* admin/CPP-DEFINES (O_RDONLY, O_RDWR, HAVE_FCNTL_H): Remove.
* admin/merge-gnulib (GNULIB_MODULES): Add fcntl-h.
* configure.ac: Do not check for fcntl.h.
* lib/gnulib.mk: Regenerate.
* lib-src/movemail.c, lib-src/update-game-score.c: Assume <fcntl.h> exists.
* nt/inc/sys/socket.h (O_NONBLOCK): Rename from O_NDELAY, since the
POSIX name for this flag is O_NONBLOCK.  All uses changed.
* nt/inc/unistd.h (O_RDWR, O_NOCTTY): New macros.  Like AT_FDCWD etc.
these really should be moved to a replacement <fcntl.h> if and
when that gets implemented.  In the meantime, include <fcntl.h>
to make sure we don't override its definitions.
* src/callproc.c (relocate_fd): Assume F_DUPFD.
* src/emacs.c, src/term.c (O_RDWR): Remove.
* src/keyboard.c (tty_read_avail_input): Use O_NONBLOCK rather than
O_NDELAY, since O_NONBLOCK is the standard name for this flag.
* src/nsterm.m: Assume <fcntl.h> exists.
* src/process.c (NON_BLOCKING_CONNECT, allocate_pty, create_process)
(create_pty, Fmake_network_process, server_accept_connection)
(wait_reading_process_output, init_process_emacs):
Assume O_NONBLOCK.
(wait_reading_process_output): Put in a special case for WINDOWSNT
to mimick the older behavior where it had O_NDELAY but not O_NONBLOCK.
It's not clear this is needed, but it's a more-conservative change.
(create_process): Assume FD_CLOEXEC.
(create_process, create_pty): Assume O_NOCTTY.
* src/sysdep.c (init_sys_modes, reset_sys_modes): Assume F_SETFL.
(reset_sys_modes): Use O_NONBLOCK rather than O_NDELAY.
Omit if not DOS_NT, since F_GETFL is not defined there.
(serial_open): Assume O_NONBLOCK and O_NOCTTY.
* src/term.c: Include <fcntl.h>, for flags like O_NOCTTY.
(O_NOCTTY): Remove.
(init_tty): Assume O_IGNORE_CTTY is defined to 0 on platforms that
lack it, since gnulib guarantees this.
* src/w32.c (fcntl): Test for O_NONBLOCK rather than O_NDELAY.

Fixes: debbugs:12881