tgba_digraph: force selection of properties kept on copy
* src/tgba/tgba.hh: Declare a prop_set to specify the types.
* src/tgba/tgbagraph.hh: Use prop_set for all copy constructors.
* iface/ltsmin/ltsmin.cc, src/bin/autfilt.cc, src/bin/randaut.cc,
src/tgbaalgos/are_isomorphic.cc, src/tgbaalgos/closure.cc,
src/tgbaalgos/complete.cc, src/tgbaalgos/degen.cc,
src/tgbaalgos/dotty.cc, src/tgbaalgos/dtgbacomp.cc,
src/tgbaalgos/dupexp.cc, src/tgbaalgos/dupexp.hh,
src/tgbaalgos/sccfilter.cc, src/tgbaalgos/simulation.cc,
src/tgbaalgos/stutterize.cc, src/tgbatest/checkpsl.cc,
src/tgbatest/emptchk.cc, src/tgbatest/ltl2tgba.cc,
wrap/python/spot.i,src/graphtest/tgbagraph.test: Adjust all uses.