Don't try to access sys.getwindowsversion unless it exists (ntpath is

imported on systems other than Windows, and in particular is imported
by test___all__; the compile farm reported that all Linux tests failed
due to this; isn't anyone in PythonDevLand running CVS on Linux?!).

Lib/ntpath.py

@@ -479,4 +479,5 @@ def abspath(path):
 # realpath is a no-op on systems without islink support
 realpath = abspath
 # Win9x family and earlier have no Unicode filename support.
-supports_unicode_filenames = sys.getwindowsversion()[3] >= 2
+supports_unicode_filenames = (hasattr(sys, "getwindowsversion") and
+                              sys.getwindowsversion()[3] >= 2)