Added a delay to deal with low time resolution on windows, which

addresses some of the windows errors. (I think the remaining failures
here and in dbopen.txt have to do with the way time is used in
management of available connections.)

src/ZODB/historical_connections.txt

@@ -41,7 +41,15 @@ We'll begin our example with a fairly standard set up.  We
     
     >>> import transaction
     >>> transaction.commit()
+
+We wait for some ttime to pass, and then make some other changes.
     
+    >>> import time
+    >>> t = time.time()
+    >>> while time.time <= t:
+    ...     time.sleep(.001)    
+
+
     >>> import datetime
     >>> now = datetime.datetime.utcnow()
     
@@ -403,4 +411,4 @@ memory usage would also be brief and unlikely to overlap.
     ...     transaction_manager=transaction1, at=now, before=historical_serial)
     Traceback (most recent call last):
     ...
-    ValueError: can only pass zero or one of `at` and `before`
\ No newline at end of file
+    ValueError: can only pass zero or one of `at` and `before`