T: improve to_vcd tracer

Make it compatible with 'template' gtwave files as found in openair's
repository.

The type VCD_NAME was added to the VCD IDs in T_messages.txt.
The database processing code was adapted to use it.
The tracer to_vcd was adapted to use it and render the produced vcd
output compatible with the 'template' gtkwave files.

When running to_vcd, do not forget to pass -vcd to use this feature.

common/utils/T/tracer/database.h

@@ -8,6 +8,7 @@ void list_ids(void *database);
 void list_groups(void *database);
 void on_off(void *d, char *item, int *a, int onoff);
 char *event_name_from_id(void *database, int id);
+char *event_vcd_name_from_id(void *_database, int id);
 int event_id_from_name(void *database, char *name);
 int number_of_ids(void *database);
 int database_get_ids(void *database, char ***ids);