* spot/parsetl/scantl.ll: Diagnose delays (##n) larger than
unbounded(). Remove all checks for delays with 1 or 2 characters.
* tests/core/parseerr.test: Add a test case.
* NEWS: Mention this fix.
Bison <3.6 used to complain about "$undefined", while Bison >=3.6 now
write "invalid token".
* tests/core/parseaut.test, tests/core/parseerr.test,
tests/core/sugar.test: Adjust expected diagnostics to match Bison pre
and post 3.6.
* tests/core/readltl.cc: Process many formulas from a
file instead of one arg at a time.
* tests/core/parse.test, tests/core/parseerr.test, tests/core/utf8.test:
Adjust to supply a file as input.
