Add some items to TODO

TODO

@@ -10,6 +10,8 @@ Cleanups
 * split modbus.c (tcp/rtu, query/response)
 * t_id in param_msqg
 * only one build_header_message function to replace build_query_packet/response_packet
+* reg_count, coil_count -> nb_points
+* avoid copies (use ptr)
 
 Documentation
 * README with a example to test the library