This gets the interface of all the functions parsing formula in line
with the interface of the automaton parser: both return a "parsed_*"
object (parsed_formula or parsed_automaton) that contains the said
object and its list of errors. Doing so avoid having to declare the
parse_error_list in advance.
* spot/tl/parse.hh, spot/parsetl/parsetl.yy: Do the change.
* spot/parsetl/fmterror.cc: Adjust the error printer.
* NEWS: Document it.
* bin/common_finput.cc, bin/common_finput.hh, bin/ltlcross.cc,
bin/ltldo.cc, bin/ltlfilt.cc, doc/org/tut01.org, doc/org/tut02.org,
doc/org/tut10.org, doc/org/tut20.org, python/ajax/spotcgi.in,
python/spot/impl.i, spot/parseaut/parseaut.yy, tests/core/checkpsl.cc,
tests/core/checkta.cc, tests/core/consterm.cc, tests/core/emptchk.cc,
tests/core/equalsf.cc, tests/core/ikwiad.cc, tests/core/kind.cc,
tests/core/length.cc, tests/core/ltlprod.cc, tests/core/ltlrel.cc,
tests/core/randtgba.cc, tests/core/readltl.cc, tests/core/reduc.cc,
tests/core/safra.cc, tests/core/syntimpl.cc, tests/core/tostring.cc,
tests/ltsmin/modelcheck.cc, tests/python/alarm.py,
tests/python/interdep.py, tests/python/ltl2tgba.py,
tests/python/ltlparse.py: Adjust all uses.
