move date_time over to boost-book

[SVN r23657]

doc/src/boost.xml

@@ -246,17 +246,7 @@
      </libraryinfo>
    </library>
 
-   <library name="Date-Time" dirname="date_time" html-only="1">
-     <libraryinfo>
-       <author>
-         <firstname>Jeff</firstname>
-         <surname>Garland</surname>
-       </author>
-
-       <librarypurpose>Date-Time library</librarypurpose>
-       <librarycategory name="category:misc"/>
-     </libraryinfo>
-   </library>
+   <xi:include href="../../libs/date_time/xmldoc/date_time.xml"/>
 
    <library name="Dynamic Bitset" dirname="dynamic_bitset" html-only="1">
      <libraryinfo>