DOCS-290 a couple of improvements to release notes

Author: Sam Kleinman

source/release-notes/2.2.txt

@@ -396,10 +396,23 @@ Additional Improvements
 use and state. In previous versions, these data were sampled. See
 :issue:`SERVER-5784` and :status:`indexCounters` for more information.
 
-``_id`` Index not Required for Updates to Capped Collections
-````````````````````````````````````````````````````````````
+``_id`` Indexes on Capped Collections
+`````````````````````````````````````
+
+All :term:`capped collections <capped collection>` now have an ``_id``
+field by default if they exist outside of the ``local`` database. This
+change only affects capped collections that using 2.2 and does not
+impact existing capped collections.
+
+Additionally in :term:`replica sets <replica set>`, :term:`secondaries
+<secondary>` will create indexes on the ``_id`` field for capped
+collections.
 
-:issue:`SERVER-4546`
+By requiring an ``_id`` field, and creating ``_id`` indexes on
+secondaries, MongoDB prevents situations where the absence of a
+``_id`` field can cause problems for replication.
+
+See: :issue:`SERVER-5516` for more information.
 
 ``localTime`` Command
 `````````````````````
@@ -432,14 +445,22 @@ Padding Specifiable on Compact Command
 Added Build Flag to Use System Libraries
 ````````````````````````````````````````
 
-Boost 1.49 Library embedded in codebase.
+The Boost library, version 1.49, is now embeded in the MongoDB
+code base.
 
 Additionally, added a flag to ``scons`` so that the build process can
-use system libraries.
+use system libraries, if desired. To build MongoDB with system
+libraries for all libraries, use the following arguments to ``scons``:
+
+.. code-block:: sh
+
+   scons --use-system-all
 
-:issue:`SERVER-3829`
+You can use the ``--use-system-boost`` to only use the system Boost
+library.
 
-:issue:`SERVER-5172`
+See the :issue:`SERVER-3829` and :issue:`SERVER-5172` issues for more
+information.
 
 Resources
 ---------