Tools for deciding the class of a formula.
* spot/tl/hierarchy.cc, spot/tl/hierarchy.hh: New files.
* spot/tl/Makefile.am: Add them.
* bin/common_output.cc, bin/common_output.hh: Implement --format=%h.
* tests/core/hierarchy.test: More tests.
* NEWS: Update.
* spot/twaalgos/remfin.cc, spot/twaalgos/remfin.hh
(rabin_to_buchi_maybe): Make this function public.
* bin/ltlfilt.cc: Implement the two options.
* tests/core/hierarchy.test: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention the new options.