added Features Within Selection option

docs/menus.sgml

@@ -170,6 +170,17 @@ selection will be discarded.
     </PARA>
   </SECT2>
 
+
+  <SECT2 ID="SELECTMENU-WITHIN-SELECTION">
+    <TITLE>Features Within Selection</TITLE>
+    <PARA>
+Select those (and only those) features that are fully contained by the currently 
+selected range of bases or any of the currently selected features. The current
+selection will be discarded.
+    </PARA>
+  </SECT2>
+
+
   <SECT2 ID="SELECTMENU-BASE-RANGE">
     <TITLE>Base Range ...</TITLE>
     <PARA>