llt2tgba_fm: fix translation of ":" in some SERE

* src/tgbaalgos/ltl2tgba_fm.cc: Here.
* src/ltltest/reduccmp.test: Add a test case.
* NEWS: Mention it.

NEWS

@@ -17,6 +17,8 @@ New in spot 1.2.3a (not yet released)
     - Fix three incorrect simplifications rules, all related to the
       factorization of Boolean subformulas in operands of the
       non-length-matching "&" SERE operator.
+    - Fix incorrect translation of the fusion operator (":") in SERE
+      such as {xx;1}:yy[*] where the left operand has 1 as tail.
 
 New in spot 1.2.3 (2014-02-11)
 

src/ltltest/reduccmp.test

@@ -348,6 +348,8 @@ for x in ../reduccmp ../reductaustr; do
      run 0 $x '{s[*]}<>->b' 'b M s'
      run 0 $x '{s[+]}<>->b' 'b M s'
      run 0 $x '{s[*2..]}<>->b' 's & X(b M s)'
+     run 0 $x '{1:a*}!' 'a'
+     run 0 $x '{(1;1):a*}!' 'Xa'
      run 0 $x '{a;b*;c;d*}<>->e' 'a & X(b U (c & (e | X(e M d))))'
      run 0 $x '{a:b*:c:d*}<>->e' 'a & ((c & (e M d)) M b)'
      run 0 $x '{a|b*|c|d*}<>->e' '((a | c) & e) | (e M b) | (e M d)'

src/tgbaalgos/ltl2tgba_fm.cc

 // -*- coding: utf-8 -*-
-// Copyright (C) 2008, 2009, 2010, 2011, 2012, 2013 Laboratoire de Recherche et
-// Développement de l'Epita (LRDE).
+// Copyright (C) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Laboratoire
+// de Recherche et Développement de l'Epita (LRDE).
 // Copyright (C) 2003, 2004, 2005, 2006 Laboratoire
 // d'Informatique de Paris 6 (LIP6), département Systèmes Répartis
 // Coopératifs (SRC), Université Pierre et Marie Curie.
@@ -912,11 +912,12 @@ namespace spot
 
 		    }
 
-		  if (dest->kind() != formula::Constant)
+		  // If the destination is not 0 or [*0], it means it
+		  // can have successors.  Fusion the tail and append
+		  // anything to concatenate.
+		  if (dest->kind() != formula::Constant
+		      || dest == ltl::constant::true_instance())
 		    {
-		      // If the destination is not a constant, it
-		      // means it can have successors.  Fusion the
-		      // tail and append anything to concatenate.
 		      const formula* dest2 =
 			multop::instance(multop::Fusion, dest, tail->clone());
 		      if (to_concat_)