* src/ltlast/binop.cc, src/ltlast/binop.hh: Introduce
EConcatMarked ("<>+>").
* src/ltlvisit/basicreduce.cc, src/ltlvisit/consterm.cc,
src/ltlvisit/lunabbrev.cc, src/ltlvisit/nenoform.cc,
src/ltlvisit/reduce.cc, src/ltlvisit/simpfg.cc,
src/ltlvisit/syntimpl.cc, src/ltlvisit/tostring.cc,
src/tgbaalgos/ltl2taa.cc, src/tgbaalgos/eltl2tgba_lacim.cc,
src/tgbaalgos/ltl2tgba_lacim.cc, src/tgba/formula2bdd.cc,
src/tgba/formula2bdd.cc: Deal with it if possible or ignore
it.