case in filenames

[René J.V. Bertin]

Hi,

Is there an official guideline concerning the use of case for distinguishing between filenames? There are (or have been) a few ports that do this for header files (or directories). In that case it's relatively easy to catch once you build on a case-insensitive FS like found on OS X (default) or MS Windows. But I just realised this might also happen with configuration or temporary files/sockets and there it would probably be less evident. 

CHeers,
R.