* Lib/macpath.py: don't return trailing colon for dirname()
(XXX won't do for volume names -- but otherwise glob(':*:*.py')
loops forever)
* Lib/traceback.py: print SyntaxError correctly
* Lib/stat.py: moved to posixstat.py; added macstat.py which has
the constants for the Mac; and created new stat.py which includes
the right one
* Lib/urllib.py: fix caching bug (by disabling the cache)
