This addresses part of #35, and is just a generalization of the rules
from 646c5170 for #263 (hence, no new documentation).
* spot/tl/simplify.cc: Implement this.
* tests/core/reduccmp.test: Add test cases.
* tests/core/stutter-tgba.test: Adjust to expect smaller automata.
Fixes#164.
* spot/twaalgos/stutter.hh, spot/twaalgos/stutter.cc: Implement
the determinization, while keeping it optional.
* NEWS: Mention the change.
* tests/core/ltl2dstar.test, tests/core/stutter-tgba.test: Add
test cases.
* tests/core/readsave.test: Adjust.