For issue #566.
* spot/twaalgos/powerset.cc: Use the edge_separator on automata
with |AP|>5 that have few distinct labels.
* tests/core/566.test: Augment test-case.
* NEWS: Update.
Related to issue #566.
* spot/twaalgos/alternation.cc (alternation_remover::run): Here.
* tests/core/566.test: Augment test case.
* NEWS: Mention the change.
For issue #566.
* spot/twaalgos/dualize.cc (dualizer::copy_edges): Implement another
loop to be used when the number of outgoing edges of a state is
smaller than the number of AP.
* tests/core/566.test: New file.
* tests/Makefile.am: Add it.
* NEWS: Mention the improvement.