Explicit bug urls make it easier to find the bug reports

CHANGES.txt

@@ -5,24 +5,28 @@ CHANGES
 3.6.1dev (unreleased)
 ---------------------
 
-- Removed usage of deprecated LayerField
+- Removed usage of deprecated LayerField.
 
-- Bug: Error thrown during __setitem__ for an ordered container leaves
-  bad key in order
+- Fixed bug: Error thrown during __setitem__ for an ordered container
+  leaves bad key in order
 
-- fixed #238579 / #163149: error with unicode traversing
+- Fixed https://bugs.launchpad.net/zope3/+bug/238579,
+  https://bugs.launchpad.net/zope3/+bug/163149: Error with unicode
+  traversing
 
-- fixed #221025 : adding menu is sorted with translated item
-                  by using a collator (better localized sorting)
+- Fixed https://bugs.launchpad.net/zope3/+bug/221025: The Adding menu
+  is sorted with translated item by using a collator (better localized
+  sorting)
 
-- fixed #227617 :
+- Fixed https://bugs.launchpad.net/zope3/+bug/227617:
     - prevent the namechooser from failing on '+', '@' and '/'
     - added tests in the namechooser
     - be sure the name chooser returns unicode
 
-- fixed #175388 : the setitem's size modification is now done in setitemf:
-  setting an existing item does not change the size,
-  and the event subscribers should see the new size instead of the old size.
+- Fixed https://bugs.launchpad.net/zope3/+bug/175388: The setitem's
+  size modification is now done in ``setitemf``: setting an existing
+  item does not change the size, and the event subscribers should see
+  the new size instead of the old size.
 
 - Reimplemented the BTreeContainer so that it directly accesses the btree
   methods (removed an old #TODO)