simplify slightly the generation of ifcName in topgen.py (preparation for later extensions)
simplify slightly the generation of ifcName in topgen.py (preparation for later extensions)

cambridgehackers/connectal,csail-csg/connectal,cambridgehackers/connectal,cambridgehackers/connectal,csail-csg/connectal,cambridgehackers/connectal,chenm001/connectal,chenm001/connectal,chenm001/connectal,hanw/connectal,hanw/connectal,cambridgehackers/connectal,csail-csg/connectal,chenm001/connectal,hanw/connectal,csail-csg/connectal,chenm001/connectal,hanw/connectal,csail-csg/connectal,hanw/connectal