+# Check whether --with-backup-prefix or --without-backup-prefix was given.
+if test "${with_backup_prefix+set}" = set; then
+ withval="$with_backup_prefix"
+ :
+fi
+
+if test x"$with_backup_prefix" != x -a x"$with_backup_prefix" != x"no"; then
+ backup_prefix="$with_backup_prefix"
+else
+ backup_prefix=","
+fi
+cat >> confdefs.h <<EOF
+#define BACKUP_PREFIX "$backup_prefix"
+EOF
+