Refactor a function for base existence

Now simply calls a function for base retrieval

Author: svorenova

src/util/std_types.h

@@ -390,17 +390,6 @@ class class_typet:public struct_typet
     bases().push_back(baset(base));
   }
 
-  bool has_base(const irep_idt &id) const
-  {
-    for(const auto &b : bases())
-    {
-      if(to_symbol_type(b.type()).get(ID_identifier)==id)
-        return true;
-    }
-
-    return false;
-  }
-
   /// Return the base with the given name, if exists.
   /// \param id The name of the base we are looking for.
   /// \return The base if exists.
@@ -417,6 +406,11 @@ class class_typet:public struct_typet
     return {};
   }
 
+  bool has_base(const irep_idt &id) const
+  {
+    return get_base(id).has_value();
+  }
+
   bool is_abstract() const
   {
     return get_bool(ID_abstract);