Update autoconf sources, in particular to better detect compiler vend…

…or. Fixes #43.

Makefile.in

@@ -1,7 +1,7 @@
-# Makefile.in generated by automake 1.16.1 from Makefile.am.
+# Makefile.in generated by automake 1.16.5 from Makefile.am.
 # @configure_input@
 
-# Copyright (C) 1994-2018 Free Software Foundation, Inc.
+# Copyright (C) 1994-2021 Free Software Foundation, Inc.
 
 # This Makefile.in is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -709,8 +709,8 @@ am__recursive_targets = \
   $(am__extra_recursive_targets)
 AM_RECURSIVE_TARGETS = $(am__recursive_targets:-recursive=) TAGS CTAGS \
 	cscope distdir distdir-am dist dist-all distcheck
-am__tagged_files = $(HEADERS) $(SOURCES) $(TAGS_FILES) \
-	$(LISP)config.h.in
+am__tagged_files = $(HEADERS) $(SOURCES) $(TAGS_FILES) $(LISP) \
+	config.h.in
 # Read a list of newline-separated strings from the standard input,
 # and print each of them once, without duplicates.  Input order is
 # *not* preserved.
@@ -727,17 +727,14 @@ am__define_uniq_tagged_files = \
   unique=`for i in $$list; do \
     if test -f "$$i"; then echo $$i; else echo $(srcdir)/$$i; fi; \
   done | $(am__uniquify_input)`
-ETAGS = etags
-CTAGS = ctags
-CSCOPE = cscope
 DIST_SUBDIRS = $(SUBDIRS)
 am__DIST_COMMON = $(srcdir)/Makefile.in $(srcdir)/config.h.in \
 	$(top_srcdir)/src/configs/foreach_config.h.in \
 	$(top_srcdir)/src/configs/foreach_config_and_type.h.in \
 	$(top_srcdir)/src/configs/foreach_type.h.in \
-	$(top_srcdir)/src/configs/include_configs.hpp.in ar-lib \
-	compile config.guess config.sub depcomp install-sh ltmain.sh \
-	missing
+	$(top_srcdir)/src/configs/include_configs.hpp.in README.md \
+	ar-lib compile config.guess config.sub depcomp install-sh \
+	ltmain.sh missing
 DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)
 distdir = $(PACKAGE)-$(VERSION)
 top_distdir = $(distdir)
@@ -776,6 +773,8 @@ am__relativize = \
 DIST_ARCHIVES = $(distdir).tar.gz
 GZIP_ENV = --best
 DIST_TARGETS = dist-gzip
+# Exists only to be overridden by the user if desired.
+AM_DISTCHECK_DVI_TARGET = dvi
 distuninstallcheck_listfiles = find . -type f -print
 am__distuninstallcheck_listfiles = $(distuninstallcheck_listfiles) \
   | sed 's|^\./|$(prefix)/|' | grep -v '$(infodir)/dir$$'
@@ -797,6 +796,8 @@ CCASFLAGS = @CCASFLAGS@
 CCDEPMODE = @CCDEPMODE@
 CFLAGS = @CFLAGS@
 CPPFLAGS = @CPPFLAGS@
+CSCOPE = @CSCOPE@
+CTAGS = @CTAGS@
 CXX = @CXX@
 CXXCPP = @CXXCPP@
 CXXDEPMODE = @CXXDEPMODE@
@@ -811,6 +812,7 @@ ECHO_C = @ECHO_C@
 ECHO_N = @ECHO_N@
 ECHO_T = @ECHO_T@
 EGREP = @EGREP@
+ETAGS = @ETAGS@
 EXEEXT = @EXEEXT@
 FGREP = @FGREP@
 GREP = @GREP@
@@ -899,6 +901,7 @@ pdfdir = @pdfdir@
 prefix = @prefix@
 program_transform_name = @program_transform_name@
 psdir = @psdir@
+runstatedir = @runstatedir@
 sbindir = @sbindir@
 sharedstatedir = @sharedstatedir@
 srcdir = @srcdir@
@@ -2673,7 +2676,6 @@ cscopelist-am: $(am__tagged_files)
 distclean-tags:
 	-rm -f TAGS ID GTAGS GRTAGS GSYMS GPATH tags
 	-rm -f cscope.out cscope.in.out cscope.po.out cscope.files
-
 distdir: $(BUILT_SOURCES)
 	$(MAKE) $(AM_MAKEFLAGS) distdir-am
 
@@ -2757,6 +2759,10 @@ dist-xz: distdir
 	tardir=$(distdir) && $(am__tar) | XZ_OPT=$${XZ_OPT--e} xz -c >$(distdir).tar.xz
 	$(am__post_remove_distdir)
 
+dist-zstd: distdir
+	tardir=$(distdir) && $(am__tar) | zstd -c $${ZSTD_CLEVEL-$${ZSTD_OPT--19}} >$(distdir).tar.zst
+	$(am__post_remove_distdir)
+
 dist-tarZ: distdir
 	@echo WARNING: "Support for distribution archives compressed with" \
 		       "legacy program 'compress' is deprecated." >&2
@@ -2799,6 +2805,8 @@ distcheck: dist
 	  eval GZIP= gzip $(GZIP_ENV) -dc $(distdir).shar.gz | unshar ;;\
 	*.zip*) \
 	  unzip $(distdir).zip ;;\
+	*.tar.zst*) \
+	  zstd -dc $(distdir).tar.zst | $(am__untar) ;;\
 	esac
 	chmod -R a-w $(distdir)
 	chmod u+w $(distdir)
@@ -2814,7 +2822,7 @@ distcheck: dist
 	    $(DISTCHECK_CONFIGURE_FLAGS) \
 	    --srcdir=../.. --prefix="$$dc_install_base" \
 	  && $(MAKE) $(AM_MAKEFLAGS) \
-	  && $(MAKE) $(AM_MAKEFLAGS) dvi \
+	  && $(MAKE) $(AM_MAKEFLAGS) $(AM_DISTCHECK_DVI_TARGET) \
 	  && $(MAKE) $(AM_MAKEFLAGS) check \
 	  && $(MAKE) $(AM_MAKEFLAGS) install \
 	  && $(MAKE) $(AM_MAKEFLAGS) installcheck \
@@ -3322,21 +3330,21 @@ uninstall-am: uninstall-iface1mincludeHEADERS \
 	clean-noinstLTLIBRARIES clean-noinstPROGRAMS cscope \
 	cscopelist-am ctags ctags-am dist dist-all dist-bzip2 \
 	dist-gzip dist-lzip dist-shar dist-tarZ dist-xz dist-zip \
-	distcheck distclean distclean-compile distclean-generic \
-	distclean-hdr distclean-libtool distclean-tags distcleancheck \
-	distdir distuninstallcheck dvi dvi-am html html-am info \
-	info-am install install-am install-data install-data-am \
-	install-dvi install-dvi-am install-exec install-exec-am \
-	install-html install-html-am install-iface1mincludeHEADERS \
-	install-iface1tincludeHEADERS install-iface1vincludeHEADERS \
-	install-iface3mincludeHEADERS install-iface3tincludeHEADERS \
-	install-info install-info-am install-libLTLIBRARIES \
-	install-man install-marrayincludeHEADERS \
-	install-memoryincludeHEADERS install-pdf install-pdf-am \
-	install-pkgincludeHEADERS install-ps install-ps-am \
-	install-stl_extincludeHEADERS install-strip \
-	install-utilincludeHEADERS installcheck installcheck-am \
-	installdirs installdirs-am maintainer-clean \
+	dist-zstd distcheck distclean distclean-compile \
+	distclean-generic distclean-hdr distclean-libtool \
+	distclean-tags distcleancheck distdir distuninstallcheck dvi \
+	dvi-am html html-am info info-am install install-am \
+	install-data install-data-am install-dvi install-dvi-am \
+	install-exec install-exec-am install-html install-html-am \
+	install-iface1mincludeHEADERS install-iface1tincludeHEADERS \
+	install-iface1vincludeHEADERS install-iface3mincludeHEADERS \
+	install-iface3tincludeHEADERS install-info install-info-am \
+	install-libLTLIBRARIES install-man \
+	install-marrayincludeHEADERS install-memoryincludeHEADERS \
+	install-pdf install-pdf-am install-pkgincludeHEADERS \
+	install-ps install-ps-am install-stl_extincludeHEADERS \
+	install-strip install-utilincludeHEADERS installcheck \
+	installcheck-am installdirs installdirs-am maintainer-clean \
 	maintainer-clean-generic mostlyclean mostlyclean-compile \
 	mostlyclean-generic mostlyclean-libtool pdf pdf-am ps ps-am \
 	tags tags-am uninstall uninstall-am \