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

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

config/move-if-change

@@ -0,0 +1,17 @@
+#!/bin/sh
+# Like mv $1 $2, but if the files are the same, just delete $1.
+# Status is 0 if $2 is changed, 1 otherwise.
+if
+test -r $2
+then
+if
+cmp -s $1 $2
+then
+echo $2 is unchanged
+rm -f $1
+else
+mv -f $1 $2
+fi
+else
+mv -f $1 $2
+fi