Make the following changes by hand, and run 'admin/merge-gnulib'.
* .gitignore: Add lib/malloc/*.gl.h.
* admin/merge-gnulib: Copy lib/af_alg.h and lib/save-cwd.h
directly from Gnulib, without worrying about Gnulib modules,
as these files are special cases.
(AVOIDED_MODULES): Remove malloc-posix.
* lib/malloc.c, lib/realloc.c, m4/malloc.m4, m4/realloc.m4:
* m4/year2038.m4: New files, copied from Gnulib.
* lib/malloca.c, lib/malloca.h:
* m4/close-stream.m4, m4/glibc21.m4, m4/malloca.m4:
Remove.  These are either no longer present in Gnulib, or are no
longer needed by modules that Emacs uses.
* oldXMenu/AddPane.c, oldXmenu/Addsel.c: Include XmenuInt.h first;
needed for new Gnulib.
* src/xmenu.c: Call emacs_abort, not abort.

Run "TZ=UTC0 admin/update-copyright".

All changes in this commit are autogenerated by running
admin/merge-gnulib.

This incorporates:
2020-08-12 stdint: port intptr_t to more-recent MinGW
2020-08-11 Use __restrict also on clang
2020-08-11 Use flexible array syntax also on clang
2020-08-11 fcntl: On native Windows, use _setmode, not setmode
* lib/binary-io.h, lib/cdefs.h, lib/fcntl.c, lib/regex.h:
* lib/stdint.in.h: Copy from Gnulib.

Run "TZ=UTC0 admin/update-copyright $(git ls-files)".

This incorporates:
2019-07-06 thread, lock, cond, tls: Remove support for Pth threads
2019-07-02 verify: document ‘assume’ better
2019-06-30 Include <stdlib.h> when needed
2019-06-30 inet_ntop, inet_pton: Avoid conflict with native Windows
* build-aux/config.sub, lib/faccessat.c, lib/fcntl.c, lib/fstatat.c:
* lib/readlinkat.c, lib/verify.h, m4/pthread_sigmask.m4:
* m4/sys_socket_h.m4: Copy from Gnulib.
* lib/gnulib.mk.in: Regenerate.

This incorporates:
2019-01-26 getloadavg: Add support for Android
2019-01-24 fchownat: Fix compilation error on Android 4.3
2019-01-24 mbtowc: Fix compilation error on Android 4.3
2019-01-24 random: Fix compilation error on Android 4.3
2019-01-24 renameat: Fix compilation error on Android 4.3
2019-01-24 unlinkat: Fix compilation error on Android 4.3
2019-01-19 gettext: support disabling use of VLAs
2019-01-17 sys_stat: Fix warning on OS/2 kLIBC
2019-01-17 fcntl: Fix syntax error (regression from 2018-10-05)
2019-01-10 verify: Enable _GL_HAVE_STATIC_ASSERT for recent G++
2018-12-22 stdioext: port to newer 32-bit Android
2018-12-16 libc-config: Support HP-UX cc in C99 mode.
* build-aux/config.guess, build-aux/config.sub, doc/misc/texinfo.tex:
* lib/cdefs.h, lib/fcntl.c, lib/getloadavg.c, lib/gettext.h:
* lib/regexec.c, lib/stdio-impl.h, lib/stdio.in.h, lib/stdlib.in.h:
* lib/sys_stat.in.h, lib/unistd.in.h, lib/verify.h, m4/stdlib_h.m4:
Copy from Gnulib.
* lib/gnulib.mk.in: Regenerate.