Update from gnulib

Update from gnulib

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.