Update the dropbear url.

I updated the dropbear url because it wasn't uploaded to network cache.
I kept an old version because :
 * our patches don't work anymore with the latest version.
 * the latest version (at the date of this commit, doesn't have an
   interesting changelog).
 * by laziness.

component/dropbear/buildout.cfg

@@ -28,7 +28,9 @@ download-only = true
 [dropbear]
 recipe = hexagonit.recipe.cmmi
 md5sum = 0284ea239083f04c8b874e08e1aca243
-url = http://matt.ucc.asn.au/dropbear/dropbear-0.53.1.tar.bz2
+# XXX: We still use an old version of dropbear instead of the last one
+#      in order have all patches working.
+url = http://matt.ucc.asn.au/dropbear/releases/dropbear-0.53.1.tar.bz2
 
 configure-options =
   --prefix=${buildout:parts-directory}/${:_buildout_section_name_}