specialize scc_filter for inherently_weak automata

Part of issue #351.

* spot/twaalgos/sccfilter.cc, spot/twaalgos/sccfilter.hh: Specialize
for inherently-weak automata.
* spot/twaalgos/postproc.cc: Simplify.
* tests/core/dca2.test, tests/core/parity2.test,
tests/core/prodor.test, tests/core/randomize.test,
tests/python/automata.ipynb, tests/python/highlighting.ipynb,
tests/python/product.ipynb, tests/python/remfin.py,
tests/python/stutter-inv.ipynb: Adjust.
* NEWS: Mention it.

tests/core/dca2.test

@@ -67,7 +67,11 @@ while read l_f; do
         autfilt -q --acceptance-is=Streett-like and.hoa
         # Streett | Streett
         autfilt r.hoa --name="($l_f)|!($r_f)" --product-or=l.hoa -S > or.hoa
-        autfilt -q -v --acceptance-is=Streett-like or.hoa
+        if ! grep -q ' weak' l.hoa; then
+            if ! grep -q ' weak' r.hoa; then
+                autfilt -q -v --acceptance-is=Streett-like or.hoa || exit 1
+            fi
+        fi
 
         autcross --language-preserved --verbose -F or.hoa -F and.hoa \
                  'autfilt %H --stats=%M | ltl2tgba >%O' \

tests/core/parity2.test

@@ -236,7 +236,7 @@ AP: 1 "a"
 acc-name: Buchi
 Acceptance: 1 Inf(0)
 properties: trans-labels explicit-labels state-acc stutter-invariant
-properties: inherently-weak
+properties: weak
 --BODY--
 State: 0
 [t] 0
@@ -270,7 +270,7 @@ AP: 1 "a"
 acc-name: Rabin 1
 Acceptance: 2 Fin(0) & Inf(1)
 properties: trans-labels explicit-labels state-acc stutter-invariant
-properties: inherently-weak
+properties: weak
 --BODY--
 State: 0
 [t] 0
@@ -304,7 +304,7 @@ AP: 1 "a"
 acc-name: Buchi
 Acceptance: 1 Inf(0)
 properties: trans-labels explicit-labels state-acc stutter-invariant
-properties: inherently-weak
+properties: weak
 --BODY--
 State: 0
 [t] 0
@@ -338,7 +338,7 @@ AP: 1 "a"
 acc-name: Streett 1
 Acceptance: 2 Fin(0) | Inf(1)
 properties: trans-labels explicit-labels state-acc colored
-properties: stutter-invariant inherently-weak
+properties: stutter-invariant weak
 --BODY--
 State: 0 {0}
 [t] 0
@@ -372,7 +372,7 @@ AP: 1 "a"
 acc-name: parity min odd 3
 Acceptance: 3 Fin(0) & (Inf(1) | Fin(2))
 properties: trans-labels explicit-labels state-acc colored
-properties: stutter-invariant inherently-weak
+properties: stutter-invariant weak
 --BODY--
 State: 0 {2}
 [t] 0
@@ -406,7 +406,7 @@ AP: 1 "a"
 acc-name: parity max even 3
 Acceptance: 3 Inf(2) | (Fin(1) & Inf(0))
 properties: trans-labels explicit-labels state-acc colored
-properties: stutter-invariant inherently-weak
+properties: stutter-invariant weak
 --BODY--
 State: 0 {1}
 [t] 0

tests/core/prodor.test

@@ -57,23 +57,24 @@ HOA: v1
 States: 3
 Start: 0
 AP: 2 "a" "b"
-Acceptance: 2 Inf(0) | Inf(1)
+acc-name: Buchi
+Acceptance: 1 Inf(0)
 properties: trans-labels explicit-labels trans-acc complete
 properties: stutter-invariant
 --BODY--
 State: 0
 [!0] 0
-[0] 0 {1}
+[0] 0 {0}
 [!0&1] 1
-[0&1] 1 {1}
+[0&1] 1 {0}
 State: 1
 [!0&1] 1 {0}
-[0&1] 1 {0 1}
+[0&1] 1 {0}
 [!0&!1] 2 {0}
-[0&!1] 2 {0 1}
+[0&!1] 2 {0}
 State: 2
 [!0] 2
-[0] 2 {1}
+[0] 2 {0}
 --END--
 EOF
 diff por.hoa exp
@@ -88,18 +89,18 @@ HOA: v1
 States: 2
 Start: 0
 AP: 2 "a" "b"
-acc-name: generalized-Buchi 2
-Acceptance: 2 Inf(0)&Inf(1)
+acc-name: Buchi
+Acceptance: 1 Inf(0)
 properties: trans-labels explicit-labels trans-acc stutter-invariant
 --BODY--
 State: 0
 [!0] 0
-[0] 0 {1}
+[0] 0
 [!0&1] 1
-[0&1] 1 {1}
+[0&1] 1
 State: 1
-[!0&1] 1 {0}
-[0&1] 1 {0 1}
+[!0&1] 1
+[0&1] 1 {0}
 --END--
 EOF
 diff pand.hoa exp

tests/core/randomize.test

@@ -1,6 +1,6 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2014, 2015, 2017 Laboratoire de Recherche et
+# Copyright (C) 2014, 2015, 2017, 2018 Laboratoire de Recherche et
 # Développement de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -33,7 +33,7 @@ AP: 4 "a" "b" "c" "d"
 acc-name: all
 Acceptance: 0 t
 properties: trans-labels explicit-labels state-acc stutter-invariant
-properties: inherently-weak
+properties: weak
 --BODY--
 State: 0
 [0] 1