Do not return const object from conversion

aconversions/src/conversions/fa2re/AbstractFAtoREConverter.h

aconversions/src/conversions/fa2re/BrzozowskiAlgebraic.cpp

aconversions/src/conversions/fa2re/BrzozowskiAlgebraic.h

aconversions/src/conversions/fa2re/StateElimination.cpp

aconversions/src/conversions/fa2re/StateElimination.h

aconversions/src/conversions/fa2rg/AbstractFAtoRGConverter.h

aconversions/src/conversions/fa2rg/FAtoLRGConverter.cpp

aconversions/src/conversions/fa2rg/FAtoLRGConverter.h

aconversions/src/conversions/fa2rg/FAtoRRGConverter.cpp

aconversions/src/conversions/fa2rg/FAtoRRGConverter.h

aconversions/src/conversions/re2fa/AbstractREtoFAConverter.h

aconversions/src/conversions/re2fa/Brzozowski.cpp

aconversions/src/conversions/re2fa/Brzozowski.h

aconversions/src/conversions/re2fa/Glushkov.cpp

aconversions/src/conversions/re2fa/Glushkov.h

aconversions/src/conversions/re2fa/Thompson.cpp

aconversions/src/conversions/re2fa/Thompson.h

aconversions/src/conversions/rg2fa/AbstractRGtoFAConverter.h

aconversions/src/conversions/rg2fa/LRGtoFAConverter.cpp

aconversions/src/conversions/rg2fa/LRGtoFAConverter.h