lib: avoid format truncation

commonio.c: In function 'commonio_unlock':
    commonio.c:487:49: warning: '.lock' directive output may be truncated writing 5 bytes into a region of size between 1 and 1024 [-Wformat-truncation=]
      487 |                 snprintf (lock, sizeof lock, "%s.lock", db->filename);
          |                                                 ^~~~~
    commonio.c:487:17: note: 'snprintf' output between 6 and 1029 bytes into a destination of size 1024
      487 |                 snprintf (lock, sizeof lock, "%s.lock", db->filename);
          |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

lib/commonio.c

@@ -467,7 +467,7 @@ static void dec_lock_count (void)
 
 int commonio_unlock (struct commonio_db *db)
 {
-	char lock[1024];
+	char lock[1029];
 
 	if (db->isopen) {
 		db->readonly = true;