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:
2020-07-07 dup2: remove support for some very old platforms
2020-07-07 memchr: remove support for some very old platforms
2020-07-04 getumask: new module
2020-07-03 getrandom: fix compilation error on native Windows
2020-07-03 lchmod: simplify after 2020-02-22 change
2020-07-01 manywarnings: improve port to GCC 10.1
2020-06-28 getrandom: fix compilation errors on older versions of mingw
2020-06-29 alloca-opt: fix warning on mingw
* lib/alloca.in.h, lib/dup2.c, lib/getrandom.c, lib/string.in.h:
* lib/sys_stat.in.h, lib/unistd.in.h, m4/dup2.m4, m4/getrandom.m4:
* m4/lchmod.m4, m4/manywarnings.m4, m4/string_h.m4, m4/sys_stat_h.m4:
* m4/unistd_h.m4: Copy from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.

This incorporates:
2020-06-28 getrandom: do not depend on ‘open’ on mingw
2020-06-28 getrandom: fix compilation errors on older versions of mingw
* build-aux/config.sub, lib/getrandom.c, m4/getrandom.m4:
Copy from Gnulib
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.

This incorporates:
2020-06-27 getloadavg: don’t depend on fopen-gnu
2020-06-25 c-dtoastr, c-ldtoastr: new modules
2020-06-01 getloadavg: fix double-increment bug
2020-06-01 tempname: use getrandom, not getentropy
2020-05-31 tempname: merge from glibc and coreutils
2020-05-31 getentropy: work around a macOS and Solaris problem
2020-05-31 fnmatch: merge from glibc
2020-05-30 unistd: remove conflicting declaration of getrandom
2020-05-30 don't assume that UNICODE is not defined
2020-05-29 fix compilation error on native Windows
2020-05-28 avoid dynamic loading of Windows API functions when possible
2020-05-28 at-internal: make more robust in multithreaded applications
2020-05-28 getloadavg: make more robust in multithreaded applications
2020-05-27 getloadavg: make more robust in multithreaded applications
2020-05-26 count-one-bits: fix MSVC specific code
2020-05-25 getentropy, getrandom: new modules
2020-05-24 open, openat: really support O_CLOEXEC
2020-05-23 verify: document ‘assume’ better
2020-05-21 regex: configure better with "clang -fsanitize=leak"
2020-05-21 memmem: configure better with "clang -fsanitize=undefined"
2020-05-19 ftoastr: fix ifndef typo
* build-aux/config.guess, build-aux/config.sub, doc/misc/texinfo.tex:
* lib/count-one-bits.h, lib/ftoastr.c, lib/ftoastr.h:
* lib/getloadavg.c, lib/gettimeofday.c, lib/libc-config.h:
* lib/open.c, lib/openat-proc.c, lib/tempname.c, lib/tempname.h:
* lib/unistd.in.h, lib/verify.h, m4/memmem.m4, m4/regex.m4:
* m4/unistd_h.m4:
Update from Gnulib.
* lib/getrandom.c, lib/sys_random.in.h:
* m4/getrandom.m4, m4/sys_random_h.m4:
New files, copied from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.