and formula::destroy.

* src/ltlast/atomic_prop.cc, src/ltlast/automatop.cc,
src/ltlast/binop.cc, src/ltlast/formula.hh, src/ltlast/formula.cc,
src/ltlast/multop.cc, src/ltlast/unop.cc, src/ltlenv/declenv.cc,
src/ltlvisit/basicreduce.cc, src/ltlvisit/clone.cc,
src/ltlvisit/destroy.cc, src/ltlvisit/nenoform.cc,
src/ltlvisit/randomltl.cc, src/ltlvisit/reduce.cc,
src/tgbatest/randtgba.cc: Adjust.