Fix coding to be utf-8 instead of UTF-8

Old UTF-8 resulted in this error from GNU Emacs:
  Warning (mule): Invalid coding system `UTF-8' is specified
  for the current buffer/file by the :coding tag.
  It is highly recommended to fix it before writing to a file.

contrib/xorg/download-xorg-7.5

@@ -1,5 +1,5 @@
 #!/usr/bin/env python
-# -*-mode: python; coding: UTF-8 -*-
+# -*-mode: python; coding: utf-8 -*-
 
 import os
 import glob