so it doesn't have to compute it.
* src/tgbaparse/tgbascan.ll: Likewise.
(YY_USER_INIT, current_file): Remove, it is too costly to use
yy::Location::filename in the current implementation
of yy::Location (this attribute is duplicated for each token).
Leaving it empty divides the parsing time by 3.
* src/tgbaparse/fmterror.cc, src/tgbaparse/public.hh
(format_tgba_parse_errors): Take the filename as argument.
* src/tgbatest/explprod.cc, src/tgbatest/ltl2tgba.cc,
src/tgbatest/mixprod.cc, src/tgbatest/powerset.cc,
src/tgbatest/readsave.cc, src/tgbatest/reductgba.cc,
src/tgbatest/tgbaread.cc, src/tgbatest/tripprod.cc,
iface/gspn/dottyssp.cc, iface/gspn/ltlgspn.cc: Adjust calls
to format_tgba_parse_errors.
(to_string_visitor::visitor(const atomic_prop*)): Use is_bare_word
to better check which atomic proposition need to be quoted.
* src/ltlparse/ltlscan.ll: Do not allow identifiers starting with F_
or G_.
* src/ltltest/equals.test, src/ltltest/tostring.test: More tests.
(subformula): Recognize `ATOMIC_PROP OP_POST_POS' and
`ATOMIC_PROP OP_POST_NEG'.
* src/ltlparse/ltlscan.ll: Introduce the not_prop start condition,
to restrict the set of atomic propositions allowed in places
where they are not expected. Make `true' and `false' case insensitive.
* src/ltltest/parse.test, src/ltltest/tostring.test: More cases.
* src/ltlvisit/tostring.cc (to_string_visitor): Quote atomic
propositions equal to "true" or "false".
