cmd-index.py: Retry os.open without O_LARGEFILE if not supported.

Python under Cygwin doesn't have os.O_LARGEFILE, so if we receive an
'AttributeError' exception trying to open something, just remove
O_LARGEFILE and try again.

cmd-index.py

@@ -6,7 +6,10 @@
 class OsFile:
     def __init__(self, path):
         self.fd = None
-        self.fd = os.open(path, os.O_RDONLY|os.O_LARGEFILE|os.O_NOFOLLOW)
+        try:
+            self.fd = os.open(path, os.O_RDONLY|os.O_LARGEFILE|os.O_NOFOLLOW)
+        except AttributeError:
+            self.fd = os.open(path, os.O_RDONLY|os.O_NOFOLLOW)
         #self.st = os.fstat(self.fd)
 
     def __del__(self):