Update manual for subject alternative name attribute of genkey task

This closes #65 pull request at github/apache/ant

manual/Tasks/genkey.html

@@ -81,6 +81,12 @@
     <td valign="top">The distinguished name for entity</td>
     <td valign="top" align="center">Yes if dname element unspecified</td>
   </tr>
+  <tr>
+    <td valign="top">saname</td>
+    <td valign="top">The subject alternative name for entity. Requires
+ Java 7 or higher.</td>
+    <td valign="top" align="center">No</td>
+  </tr>
   <tr>
     <td valign="top">validity</td>
     <td valign="top">(integer) indicates how many days certificate is valid</td>