Trezor: Matrix recovery support

New Trezor firmware has matrix recovery support, which is a new
recovery method that doesn't leak the entered words.

plugins/trezor/clientbase.py

@@ -84,6 +84,15 @@ class GuiMixin(object):
         return self.proto.PassphraseStateAck()
 
     def callback_WordRequest(self, msg):
+        if (msg.type is not None
+            and msg.type in (self.types.WordRequestType_Matrix9,
+                             self.types.WordRequestType_Matrix6)):
+            num = 9 if msg.type == self.types.WordRequestType_Matrix9 else 6
+            char = self.handler.get_matrix(num)
+            if (char == 'x'):
+                return self.proto.Cancel()
+            return self.proto.WordAck(word=char)
+
         self.step += 1
         msg = _("Step {}/24.  Enter seed word as explained on "
                 "your {}:").format(self.step, self.device)