Netlist cannot handle the same component name from 2 different libs

[guitorri]

See #594 for context.

Components from system and user libraries are placed as follows in the schematic.

User lib

<Qucs Schematic 0.0.19>
<Components>
  <Lib T 1 0 0 8 -26 0 0 "/Users/guitorri/qucs_area/_demo/user_lib/NMOSFETs" 0 "2N7000" 0>
</Components>

System lib

<Qucs Schematic 0.0.19>
<Components>
  <Lib T 1 0 0 8 -26 0 0 "NMOSFETs" 0 "2N7000" 0>
</Components>

These two components will be netlisted twice with the same subcirtcuit name:

.Def:NMOSFETs_2N7000 _net4 _net3 _net5
...
.Def:NMOSFETs_2N7000 _net4 _net3 _net5
...

Which is rejected by qucsator:
checker error, found 2 definitions of 'Def:NMOSFETs_2N7000'