* src/ltlast/automatop.cc, src/ltlast/automatop.hh,
src/ltlast/binop.cc, src/ltlast/binop.hh, src/ltlast/multop.cc,
src/ltlast/multop.hh, src/ltlast/unop.cc, src/ltlast/unop.hh:
Add a dump_instance() static method to all class.
* src/ltltest/readltl.cc: Add option -r to dump all instances
with their reference count, after parsing and after deletion.