Add missing vistor implementations to visitors.h (#2539)

Notably, set_all_bn_running_stats_window_sizes and fuse_layers.

But also I took the chance to remove the superflous separators and
change the attribute of upsample layers from stride to scale.

dlib/dnn/layers.h

@@ -1708,136 +1708,6 @@ namespace dlib
     template <typename SUBNET>
     using bn_fc = add_layer<bn_<FC_MODE>, SUBNET>;
 
-// ----------------------------------------------------------------------------------------
-
-    namespace impl
-    {
-        class visitor_bn_running_stats_window_size
-        {
-        public:
-
-            visitor_bn_running_stats_window_size(unsigned long new_window_size_) : new_window_size(new_window_size_) {}
-
-            template <typename T>
-            void set_window_size(T&) const
-            {
-                // ignore other layer detail types
-            }
-
-            template < layer_mode mode >
-            void set_window_size(bn_<mode>& l) const
-            {
-                l.set_running_stats_window_size(new_window_size);
-            }
-
-            template<typename input_layer_type>
-            void operator()(size_t , input_layer_type& )  const
-            {
-                // ignore other layers
-            }
-
-            template <typename T, typename U, typename E>
-            void operator()(size_t , add_layer<T,U,E>& l)  const
-            {
-                set_window_size(l.layer_details());
-            }
-
-        private:
-
-            unsigned long new_window_size;
-        };
-
-        class visitor_disable_input_bias
-        {
-        public:
-
-            template <typename T>
-            void disable_input_bias(T&) const
-            {
-                // ignore other layer types
-            }
-
-            // handle the standard case
-            template <typename U, typename E>
-            void disable_input_bias(add_layer<layer_norm_, U, E>& l)
-            {
-                disable_bias(l.subnet().layer_details());
-                set_bias_learning_rate_multiplier(l.subnet().layer_details(), 0);
-                set_bias_weight_decay_multiplier(l.subnet().layer_details(), 0);
-            }
-
-            template <layer_mode mode, typename U, typename E>
-            void disable_input_bias(add_layer<bn_<mode>, U, E>& l)
-            {
-                disable_bias(l.subnet().layer_details());
-                set_bias_learning_rate_multiplier(l.subnet().layer_details(), 0);
-                set_bias_weight_decay_multiplier(l.subnet().layer_details(), 0);
-            }
-
-            // handle input repeat layer case
-            template <layer_mode mode, size_t N, template <typename> class R, typename U, typename E>
-            void disable_input_bias(add_layer<bn_<mode>, repeat<N, R, U>, E>& l)
-            {
-                disable_bias(l.subnet().get_repeated_layer(0).layer_details());
-                set_bias_learning_rate_multiplier(l.subnet().get_repeated_layer(0).layer_details(), 0);
-                set_bias_weight_decay_multiplier(l.subnet().get_repeated_layer(0).layer_details(), 0);
-            }
-
-            template <size_t N, template <typename> class R, typename U, typename E>
-            void disable_input_bias(add_layer<layer_norm_, repeat<N, R, U>, E>& l)
-            {
-                disable_bias(l.subnet().get_repeated_layer(0).layer_details());
-                set_bias_learning_rate_multiplier(l.subnet().get_repeated_layer(0).layer_details(), 0);
-                set_bias_weight_decay_multiplier(l.subnet().get_repeated_layer(0).layer_details(), 0);
-            }
-
-            // handle input repeat layer with tag case
-            template <layer_mode mode, unsigned long ID, typename E>
-            void disable_input_bias(add_layer<bn_<mode>, add_tag_layer<ID, impl::repeat_input_layer>, E>& )
-            {
-            }
-
-            template <unsigned long ID, typename E>
-            void disable_input_bias(add_layer<layer_norm_, add_tag_layer<ID, impl::repeat_input_layer>, E>& )
-            {
-            }
-
-            // handle tag layer case
-            template <layer_mode mode, unsigned long ID, typename U, typename E>
-            void disable_input_bias(add_layer<bn_<mode>, add_tag_layer<ID, U>, E>& )
-            {
-            }
-
-            template <unsigned long ID, typename U, typename E>
-            void disable_input_bias(add_layer<layer_norm_, add_tag_layer<ID, U>, E>& )
-            {
-            }
-
-            // handle skip layer case
-            template <layer_mode mode, template <typename> class TAG, typename U, typename E>
-            void disable_input_bias(add_layer<bn_<mode>, add_skip_layer<TAG, U>, E>& )
-            {
-            }
-
-            template <template <typename> class TAG, typename U, typename E>
-            void disable_input_bias(add_layer<layer_norm_, add_skip_layer<TAG, U>, E>& )
-            {
-            }
-
-            template<typename input_layer_type>
-            void operator()(size_t , input_layer_type& ) const
-            {
-                // ignore other layers
-            }
-
-            template <typename T, typename U, typename E>
-            void operator()(size_t , add_layer<T,U,E>& l)
-            {
-                disable_input_bias(l);
-            }
-        };
-    }
-
 // ----------------------------------------------------------------------------------------
 
     enum fc_bias_mode