Add Portable Library Tools to dependency list.

Author: mrward

doc/Dependencies.html

@@ -63,6 +63,10 @@
 				<td style="padding-right: 8px;">.NET Framework 3.5 SP1 and below</td>
 				<td>Included with .NET framework</td>
 			</tr>
+			<tr>
+				<td>.NET Portable Class Libraries</td>
+				<td><a href="http://visualstudiogallery.msdn.microsoft.com/b0e0b5e9-e138-410b-ad10-00cb3caf4981/">Portable Library Tools - Install with the /buildmachine switch</a></td>
+			</tr>
 		</table>
 
 		<p>