Handle split rename events on Windows

[smashwilson]

If the FILE_ACTION_RENAMED_OLD_NAME and FILE_ACTION_RENAMED_NEW_NAME events are delivered to the event callback in separate batches on Windows, the rename won't be correlated correctly, even though we should be able to. It looks like this is happening about half of the time:

renamed total: 912
 - exact: 435 (47.69%)
 - unknown: 0 (0%)
 - split exact: 0 (0%)
 - split half unknown: 477 (52.3%)
 - split full unknown: 0 (0%)
 - unexpected: 0 (0%)
 - missed: 0 (0%)