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".

This incorporates:
2020-07-30 work around some Oracle Studio attribute bugs
2020-07-29 fsusage, regex, stat-size: remove Cray support
2020-07-26 inttypes: remove support for AIX 4
2020-07-26 gettimeofday: remove workaround for Mac OS X 10.0
2020-07-26 don't require gl_LOCALTIME_BUFFER_DEFAULTS
2020-07-26 alloca: remove Cray-2 and Cray Y-MP support
2020-07-26 libgmp: remove dependency on havelib
2020-07-26 libgmp: remove HAVE_GMP, LIB_GMP
2020-07-25 multiarch: prepare for x86_64+arm64 universal in macOS 11
2020-07-25 sigprocmask: small autoconf macro improvement
2020-07-25 small autoconf macro improvements
2020-07-24 timespec: remove dependence on ‘verify’
2020-07-24 optimize a few more three-valued comparisons
2020-07-24 fix _GL_CMP parenthesization typo
2020-07-23 optimize three-valued comparison between integers
2020-07-24 doc: update for Mac OS X 10.13
2020-07-23 fchmodat, lchmod: use /proc on Cygwin
2020-07-21 inttypes: fix PRI*PTR and SCN*PTR on 64-bit native Windows
2020-07-12 libgmp: avoid warning when --without-libgmp is used
2020-07-12 libgmp: link to the correct shared library
* lib/mini-gmp-gnulib.c: Ignore -Wsuggest-attribute=malloc only for
* build-aux/config.guess, build-aux/config.sub:
* build-aux/install-sh, doc/misc/texinfo.tex, lib/c-strcasecmp.c:
* lib/c-strncasecmp.c, lib/fchmodat.c, lib/fsusage.c:
* lib/gettimeofday.c, lib/inttypes.in.h, lib/lchmod.c:
* lib/mini-gmp-gnulib.c, lib/nstrftime.c, lib/regex.h, lib/timespec.h:
* m4/alloca.m4, m4/getgroups.m4, m4/gettimeofday.m4:
* m4/gnulib-common.m4, m4/inttypes.m4, m4/libgmp.m4, m4/mktime.m4:
* m4/multiarch.m4:
Copy from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/Makefile.in, test/Makefile.in (LIBGMP):
Rename from LIB_GMP for compatibility with Gnulib.
All uses changed.

This incorporates:
2019-12-23 mktime, nstrftime: tweak division performance
2019-12-22 count-leading-zeros: assume 'long long'
2019-12-22 count-one-bits: assume 'long long'
2019-12-22 count-trailing-zeros: assume 'long long'
2019-12-12 inttypes-incomplete: assume 'long long'
2019-12-22 malloca: assume 'long long'
2019-12-22 stdint: assume 'long long'
2019-12-22 strtoll, strtoimax, strtoumax: assume 'long long'
2019-12-22 prefer lib_SOURCES to unconditional AC_LIBOBJ
2019-12-19 nstrftime: avoid a shadowing warning
2019-12-18 improve port of AC_C_RESTRICT to Oracle C++
2019-12-12 stdalign: port to xlclang 16.01
2019-12-11 stddef, unistd: fix compilation error in C++ mode on MSVC
2019-12-08 fix compilation errors in C++ mode on Haiku
2019-12-08 fix compilation errors in 32-bit C++ mode on HP-UX 11/ia64
2019-12-08 fix compilation error in C++ mode on OpenBSD
* build-aux/config.guess, doc/misc/texinfo.tex:
* lib/count-leading-zeros.h, lib/count-one-bits.h:
* lib/count-trailing-zeros.h, lib/inttypes.in.h, lib/malloca.h:
* lib/mktime.c, lib/nstrftime.c, lib/signal.in.h, lib/stdalign.in.h:
* lib/stddef.in.h, lib/stdint.in.h, lib/stdio.in.h, lib/stdlib.in.h:
* lib/strtoimax.c, lib/unistd.in.h, m4/gnulib-common.m4:
* m4/inttypes.m4, m4/largefile.m4, m4/malloca.m4, m4/strtoimax.m4:
* m4/strtoll.m4:
Copy from Gnulib.  Also, change copyright notices in some other
Gnulib-copied files to exactly match Gnulib, as Gnulib updated
them in a trivially different way.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.

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

This incorporates mostly just copyright-year changes, plus
recent minor updates from glibc for the non-Emacs regular
expression code.