remove some unused variables

as reported by cppcheck

* src/taalgos/emptinessta.cc, src/taalgos/tgba2ta.cc, src/twa/acc.cc,
src/twaalgos/minimize.cc, src/twaalgos/neverclaim.cc,
src/twaalgos/remprop.cc, src/twaalgos/sccinfo.cc: Here.

src/taalgos/emptinessta.cc

@@ -1,6 +1,6 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2010, 2011, 2012, 2013, 2014 Laboratoire de Recherche
+// Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015 Laboratoire de
-// et Développement de l'Epita (LRDE).
+// Recherche et Développement de l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
 //
@@ -71,9 +71,6 @@ namespace spot
     //   it is also used as a key in H.
     std::stack<pair_state_iter> todo;
 
-    std::unordered_map<const state*, std::string,
-		       state_ptr_hash, state_ptr_equal> colour;
-
     trace
       << "PASS 1" << std::endl;
 
@@ -159,7 +156,6 @@ namespace spot
                 inc_depth();
 
                 // set the h value of the Backtracked state to negative value.
-                // colour[curr] = BLUE;
                 i->second = -std::abs(i->second);
 
                 // Backtrack livelock_roots.
@@ -175,7 +171,7 @@ namespace spot
                   {
                     // removing states
                     for (auto j: scc.rem())
-		      h[j] = -1; //colour[*i] = BLACK;
+		      h[j] = -1;
                     dec_depth(scc.rem().size());
                     scc.pop();
                     assert(!arc.empty());
@@ -227,7 +223,6 @@ namespace spot
                 ta_succ_iterator_product* iter = a_->succ_iter(dest);
                 iter->first();
                 todo.emplace(dest, iter);
-                //colour[dest] = GREY;
                 inc_depth();
 
                 //push potential root of live-lock accepting cycle
@@ -329,7 +324,6 @@ namespace spot
                     return true;
                   }
 
-                std::set<const state*, state_ptr_less_than>::const_iterator it;
                 for (const state* succ: liveset_dest)
 		  if (heuristic_livelock_detection(succ, h, h_livelock_root,
 						   liveset_curr))
@@ -357,7 +351,7 @@ namespace spot
   {
     int hu = h[u];
 
-    if (hu > 0) // colour[u] == GREY
+    if (hu > 0)
       {
 
         if (hu >= h_livelock_root)

src/taalgos/tgba2ta.cc

@@ -241,7 +241,6 @@ namespace spot
 		  if (sscc.top().index == i->second)
 		    {
 		      // removing states
-		      std::list<state*>::iterator i;
 		      bool is_livelock_accepting_sscc = (sscc.rem().size() > 1)
 			&& ((sscc.top().is_accepting) ||
 			    (testing_aut->acc().

src/twa/acc.cc

@@ -355,7 +355,6 @@ namespace spot
       auto sz = c->size;
       auto start = c - sz - 1;
       auto op = c->op;
-      std::set<acc_cond::acc_code> res;
       switch (op)
 	{
 	case acc_cond::acc_op::Or:

src/twaalgos/minimize.cc

@@ -145,7 +145,6 @@ namespace spot
 
     for (sit = sets.begin(); sit != sets.end(); ++sit)
       {
-	hash_set::iterator hit;
 	hash_set* h = *sit;
 
 	// Pick one state.

src/twaalgos/neverclaim.cc

@@ -106,7 +106,6 @@ namespace spot
       void
       print_state(unsigned n) const
       {
-	std::string label;
 	bool acc = aut_->state_is_accepting(n);
 	if (n == aut_->get_init_state_number())
 	  {

src/twaalgos/remprop.cc

@@ -58,7 +58,6 @@ namespace spot
   void remove_ap::add_ap(const char* arg)
   {
     auto& env = spot::ltl::default_environment::instance();
-    std::vector<const spot::ltl::atomic_prop*> group;
     auto start = arg;
     while (*start)
       {

src/twaalgos/sccinfo.cc

@@ -52,8 +52,6 @@ namespace spot
 
     typedef std::list<scc> stack_type;
     stack_type root_;		// Stack of SCC roots.
-    std::stack<std::pair<bdd, bdd>> arc_; // A stack of acceptance conditions
-				// between each of these SCC.
     std::vector<int> h_(n, 0);
     // Map of visited states.  Values > 0 designate maximal SCC.
     // Values < 0 number states that are part of incomplete SCCs being