Here's a tiny patch that just changes normcase->normpath.  This fixes the casing issue at the 'gettempdir' level, though it doesn't address the 'normcase' function itself.

Note that *both* macpath.py and ntpath.py use <s>.lower, which obviously won't fly on case-sensitive mounts. If someone more experienced than I has a suggestion on how to handle that -- or whether its worthwhile to even touch -- I'll gladly implement.