Mention mustek_pro backend.

unsupported/mustek-bearpaw-2448ta-pro.html

@@ -35,6 +35,11 @@
       SQ scanner controller chip.
     </p>
     <h2>Comments</h2>
+    <p>
+      Actually <a
+      href="http://www.meier-geinitz.de/sane/mustek_pro-backend/">there is a
+      backend now</a> (untested).
+    </p>
     <p>
       Similar to Mustek BearPaw 2400 TA Pro?
     </p>