* spot/twaalgos/couvreurnew.cc, spot/twaalgos/gv04.cc,
spot/twaalgos/magic.cc, spot/twaalgos/se05.cc, spot/twaalgos/tau03.cc,
spot/twaalgos/tau03opt.cc: Throw if precondition on acceptance
condition is not satisfied.
* tests/python/misc-ec.py: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention the change.
