allow scc_filter() and scc_filter_states() on any TωA

Note however that scc_info does not provide a precise accept/reject
characterization for SCCs when using Fin acceptance.  However whenever
it tells that an SCC is rejecting, scc_filter_states() may safely remove
it.

* src/twaalgos/sccfilter.cc (scc_filter_states): Allow on any TωA.
(scc_filter): Only use acceptance simplifications on TGBA.
* src/tests/unambig.test: Add a co-Büchi test.

src/tests/unambig.test

@@ -82,6 +82,19 @@ State: 0
 State: 1
 [0] 1 {0}
 --END--
+HOA: v1
+States: 2
+Start: 0
+AP: 2 "a" "b"
+Acceptance: 1 Fin(0)
+--BODY--
+State: 0
+[0] 1 {0}
+[1] 1
+State: 1
+[0] 1 {0}
+[!0] 1
+--END--
 EOF
 
 run 1 $autfilt -q --is-unambiguous input