+dnl Set the backup prefix
+undefine([backup-prefix])dnl
+AC_ARG_WITH([backup-prefix],
+ [ --with-backup-prefix=, set the backup prefix [,]])
+if test x"$with_backup_prefix" != x -a x"$with_backup_prefix" != x"no"; then
+ backup_prefix="$with_backup_prefix"
+else
+ backup_prefix=","
+fi
+AC_DEFINE_UNQUOTED(BACKUP_PREFIX, "$backup_prefix")dnl
+