Replace symex field by namespace

symex was only used for its namespace.

Author: romainbrenguier

src/goto-symex/symex_dereference.cpp

@@ -276,7 +276,7 @@ void goto_symext::dereference_rec(
     dereference_rec(tmp1, state, guard, false);
 
     // we need to set up some elaborate call-backs
-    symex_dereference_statet symex_dereference_state(*this, state);
+    symex_dereference_statet symex_dereference_state(ns, state);
 
     value_set_dereferencet dereference(
       ns,

src/goto-symex/symex_dereference_state.cpp

@@ -17,8 +17,6 @@ bool symex_dereference_statet::has_failed_symbol(
   const exprt &expr,
   const symbolt *&symbol)
 {
-  const namespacet &ns=goto_symex.ns;
-
   if(expr.id()==ID_symbol &&
      expr.get_bool(ID_C_SSA_symbol))
   {
@@ -72,7 +70,7 @@ void symex_dereference_statet::get_value_set(
   const exprt &expr,
   value_setst::valuest &value_set)
 {
-  state.value_set.get_value_set(expr, value_set, goto_symex.ns);
+  state.value_set.get_value_set(expr, value_set, ns);
 
   #if 0
   std::cout << "**************************\n";

src/goto-symex/symex_dereference_state.h

@@ -21,15 +21,15 @@ class symex_dereference_statet:
 {
 public:
   symex_dereference_statet(
-    goto_symext &_goto_symex,
+    namespacet &ns,
     goto_symext::statet &_state):
-    goto_symex(_goto_symex),
+    ns(ns),
     state(_state)
   {
   }
 
 protected:
-  goto_symext &goto_symex;
+  namespacet &ns;
   goto_symext::statet &state;
 
   void get_value_set(