Added ???_R and ???_D macros to reference

[SVN r12910]

doc/reference/arithmetic_add.htm

@@ -44,6 +44,10 @@ single token).</p>
 
 <hr>
 
+<h2><a name="BOOST_PP_ADD_D">#define BOOST_PP_ADD_D</a>(D,X,Y)</h2>
+ <p>Can be used inside <a href="while.htm#BOOST_PP_WHILE">BOOST_PP_WHILE</a>().</p> 
+<hr>
+
 <h2><a name="BOOST_PREPROCESSOR_ADD">#define BOOST_PREPROCESSOR_ADD</a>(X,Y)</h2>
  <p>Obsolete. Use <a href="arithmetic_add.htm#BOOST_PP_ADD">BOOST_PP_ADD</a>().</p> 
 <hr>