schema-check: Ignore hidden files

Otherwise, the parser will croak when it comes across temporary files
such as vim's .*.swp files.

utils/schema-check/dn42-schema.py

@@ -354,6 +354,8 @@ def __index_files(path, use_file):
           continue
 
         for f in files:
+            if f[0] == ".":
+                continue
             dom = FileDOM(os.path.join(root, f))
             yield dom