Mention that these scanners are supported by hp3500 backend.

unsupported/hp-scanjet-3500c.html

@@ -36,6 +36,10 @@
 	RTS8801C2-6</a>
     </p>
     <h2>Comments</h2>
+    <p>
+      Actually this scanner is now supported by the <a
+      href="http://projects.troy.rollo.name/rt-scanners/">hp3500 backend</a>.
+    </p>
     <p>
       <a href="http://www.cscs.ch/~tack/hp3530.html">Someone started working on the 3500 series</a>
     </p>

unsupported/hp-scanjet-3530c.html

@@ -36,6 +36,10 @@
       21176A1<br>
     </p>
     <h2>Comments</h2>
+    <p>
+      Actually this scanner is now supported by the <a
+      href="http://projects.troy.rollo.name/rt-scanners/">hp3500 backend</a>.
+    </p>
     <p>
       <a href="http://www.cscs.ch/~tack/hp3530.html">Someone started working on that scanner</a>
     </p>