postproc: add a SBAcc option

Producing state-based acceptance is now part of the postprocessing
routines.  That means we can more easily simplify automata with
state-based acceptance (using autfilt -S --small --high, for instance)
and as as side-effect, ltl2tgba can produce GBA.  However the result of
ltl2tgba -S is often larger than that of ltl2tgba -B.

* src/twaalgos/postproc.cc, src/twaalgos/postproc.hh: Implement
the SBAcc option.
* src/bin/common_post.cc, src/bin/common_post.hh: Implement -S.
* src/bin/autfilt.cc, src/bin/dstar2tgba.cc, src/bin/ltl2tgba.cc,
src/bin/ltl2tgta.cc, src/bin/ltldo.cc: Adjust.
* src/tests/sim3.test: Augment test case.
* NEWS, doc/org/ltl2tgba.org, doc/org/autfilt.org: Document it -S.

src/tests/sim3.test

@@ -47,3 +47,40 @@ State: 6 {0 3}
 EOF
 
 test "`../../bin/autfilt --small input --stats=%S,%s`" = 7,5
+
+../../bin/autfilt -S --high --small input -H > out
+cat >expected <<EOF
+HOA: v1
+States: 5
+Start: 0
+AP: 2 "b" "a"
+Acceptance: 4 (Fin(0) & Inf(1)) | (Fin(2) & Inf(3))
+properties: trans-labels explicit-labels state-acc complete
+properties: deterministic
+--BODY--
+State: 0 {0}
+[!1] 1
+[1] 3
+State: 1 {1 3}
+[0&!1] 1
+[!0&!1] 2
+[0&1] 3
+[!0&1] 4
+State: 2 {1}
+[0&!1] 1
+[!0&!1] 2
+[0&1] 3
+[!0&1] 4
+State: 3 {0 3}
+[0&!1] 1
+[!0&!1] 2
+[0&1] 3
+[!0&1] 4
+State: 4 {0}
+[0&!1] 1
+[!0&!1] 2
+[0&1] 3
+[!0&1] 4
+--END--
+EOF
+diff out expected