Merge revs 40664 & 40667 from the trunk.

Nail the type of oids, as agreed ;-) to in

 http://mail.zope.org/pipermail/zodb-dev/2005-March/008593.html

NEWS.txt

 What's new in ZODB3 3.6b5?
 ==========================
-Release date: 04-Dec-2005
+Release date: DD-MMM-2005
 
 Following is combined news from internal releases (to support ongoing
 Zope3 development).  These are the dates of the internal releases:
 
+- 3.6b5 DD-MMM-2005
 - 3.6b4 04-Dec-2005
 - 3.6b3 06-Nov-2005
 - 3.6b2 25-Oct-2005
@@ -68,6 +69,9 @@ Persistent
   (unghostified), and its state is changed from the ghost state to the
   changed state.  The new behavior is less surprising and more robust.
 
+- (3.6b5) The documentation for ``_p_oid`` now specifies the concrete
+  type of oids (in short, an oid is either None or a non-empty string).
+
 Commit hooks
 ------------
 

src/persistent/interfaces.py

@@ -167,7 +167,9 @@ class IPersistent(Interface):
 
         It is up to the data manager to assign this.
         The special value None is reserved to indicate that an object
-        id has not been assigned.  Non-None object ids must be strings.
+        id has not been assigned.  Non-None object ids must be non-empty
+        strings.  The 8-byte string '\0'*8 (8 NUL bytes) is reserved to
+        identify the database root object.
         """)
 
     _p_changed = Attribute(