Enable network % output() of rnn_layer

Author: milancurcic

src/nf/nf_network_submodule.f90

@@ -15,6 +15,7 @@
   use nf_loss, only: quadratic_derivative
   use nf_optimizers, only: optimizer_base_type, sgd
   use nf_parallel, only: tile_indices
+  use nf_rnn_layer, only: rnn_layer
   use nf_activation, only: activation_function, &
                            elu, &
                            exponential, &
@@ -391,6 +392,8 @@ module function predict_1d(self, input) result(res)
         res = output_layer % output
       type is(flatten_layer)
         res = output_layer % output
+      type is(rnn_layer)
+        res = output_layer % output
       class default
         error stop 'network % output not implemented for this output layer'
     end select