* src/ltlast/unop.cc (NegClosure): Reset is.not_marked.
* src/ltlvisit/mark.hh,
src/ltlvisit/mark.cc (has_mark_visitor, has_mark): Remove.
* src/tgbaalgos/ltl2tgba_fm.cc: Use f->is_marked() instead
of has_mark(f).