control_hs.h: use a couple of struct delcarations

Doing this frees us from some assumptions about include order.

src/feature/control/control_hs.h

@@ -11,23 +11,24 @@
 #ifndef TOR_CONTROL_HS_H
 #define TOR_CONTROL_HS_H
 
+struct control_connection_t;
 struct control_cmd_syntax_t;
+struct control_cmd_args_t;
 
 extern const struct control_cmd_syntax_t onion_client_auth_add_syntax;
 extern const struct control_cmd_syntax_t onion_client_auth_remove_syntax;
 extern const struct control_cmd_syntax_t onion_client_auth_view_syntax;
 
 int
-handle_control_onion_client_auth_add(control_connection_t *conn,
-                                     const control_cmd_args_t *args);
+handle_control_onion_client_auth_add(struct control_connection_t *conn,
+                                     const struct control_cmd_args_t *args);
 
 int
-handle_control_onion_client_auth_remove(control_connection_t *conn,
-                                        const control_cmd_args_t *args);
+handle_control_onion_client_auth_remove(struct control_connection_t *conn,
+                                        const struct control_cmd_args_t *args);
 
 int
-handle_control_onion_client_auth_view(control_connection_t *conn,
-                                      const control_cmd_args_t *args);
+handle_control_onion_client_auth_view(struct control_connection_t *conn,
+                                      const struct control_cmd_args_t *args);
 
 #endif
-