* Makefile.maint, GNUmakefile: New, from Autoconf 2.52.

* config/prev-version.txt, config/move-if-change: New.
* Makefile.am: Adjust.

GNUmakefile

@@ -0,0 +1,32 @@
+# Having a separate GNUmakefile lets me `include' the dynamically
+# generated rules created via Makefile.maint as well as Makefile.maint itself.
+# This makefile is used only if you run GNU Make.
+# It is necessary if you want to build targets usually of interest
+# only to the maintainer.
+
+# Systems where /bin/sh is not the default shell need this.  The $(shell)
+# command below won't work with e.g. stock DOS/Windows shells.
+SHELL = /bin/sh
+
+have-Makefile := $(shell test -f Makefile && echo yes)
+
+# If the user runs GNU make but has not yet run ./configure,
+# give them a diagnostic.
+ifeq ($(have-Makefile),yes)
+
+include Makefile
+include $(srcdir)/Makefile.maint
+
+else
+
+all:
+	@echo There seems to be no Makefile in this directory.
+	@echo "You must run ./configure before running \`make'."
+	@exit 1
+
+endif
+
+# Tell version 3.79 and up of GNU make to not build goals in this
+# directory in parallel.  This is necessary in case someone tries to
+# build multiple targets on one command line.
+.NOTPARALLEL: