build: update autoconf files

Issue #55

Makefile.in

@@ -1,4 +1,4 @@
-# Makefile.in generated by automake 1.16.2 from Makefile.am.
+# Makefile.in generated by automake 1.16.3 from Makefile.am.
 # @configure_input@
 
 # Copyright (C) 1994-2020 Free Software Foundation, Inc.
@@ -241,6 +241,8 @@ am__relativize = \
 DIST_ARCHIVES = $(distdir).tar.gz $(distdir).tar.xz
 GZIP_ENV = --best
 DIST_TARGETS = dist-xz 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$$'
@@ -815,7 +817,7 @@ distcheck: dist
 	    $(DISTCHECK_CONFIGURE_FLAGS) \
 	    --srcdir=../.. --prefix="$$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 \