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.