Add IEnumerable.GetEnumerator description

Author: Jan Jahoda

xml/System.Net/WebHeaderCollection.xml

@@ -2000,8 +2000,8 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Returns an enumerator that can iterate through the <see cref="T:System.Net.WebHeaderCollection" /> instance.</summary>
+        <returns>An <see cref="T:System.Collections.IEnumerator" /> for the <see cref="T:System.Net.WebHeaderCollection" />.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>