Deprecate ltl::clone(f) in favor of f->clone().
* src/ltlvisit/clone.hh (clone): Document and declare as deprecated.
* src/ltlast/formula_tree.cc, src/ltlvisit/basicreduce.cc,
src/ltlvisit/clone.cc, src/ltlvisit/contain.cc,
src/ltlvisit/lunabbrev.cc, src/ltlvisit/reduce.cc,
src/ltlvisit/syntimpl.cc, src/tgba/bdddict.cc,
src/tgba/formula2bdd.cc, src/tgba/tgbabddconcretefactory.cc,
src/tgbaalgos/ltl2taa.cc, src/tgbaalgos/ltl2tgba_fm.cc,
src/tgbatest/complementation.cc, wrap/python/tests/ltlsimple.py:
Adjust clone() usage, and remove the #include "clone.hh" when
appropriate.
48fb19ea44