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This incorporates:
2017-09-16 manywarnings: port to GCC on 64-bit MS-Windows
2017-09-13 all: Replace many more http URLs by https URLs
* build-aux/config.guess, build-aux/config.sub:
* build-aux/gitlog-to-changelog, doc/misc/texinfo.tex:
* lib/allocator.h, lib/count-leading-zeros.h:
* lib/count-trailing-zeros.h, lib/dup2.c, lib/filevercmp.c:
* lib/fstatat.c, lib/fsync.c, lib/ftoastr.c, lib/ftoastr.h:
* lib/intprops.h, lib/signal.in.h, lib/stdio-impl.h, lib/stdio.in.h:
* lib/unistd.in.h, lib/utimens.c, m4/alloca.m4, m4/extern-inline.m4:
* m4/fstatat.m4, m4/gnulib-common.m4, m4/manywarnings.m4:
* m4/std-gnu11.m4, m4/sys_types_h.m4, m4/vararrays.m4:
Copy from Gnulib.
* lib/gnulib.mk.in: Regenerate.