Use item->set_charset() instead of item->str_value.set_charset()

sql/item.cc

@@ -132,7 +132,7 @@ void Item_field::set_field(Field *field_par)
   table_name=field_par->table_name;
   field_name=field_par->field_name;
   unsigned_flag=test(field_par->flags & UNSIGNED_FLAG);
-  str_value.set_charset(field_par->charset());
+  set_charset(field_par->charset());
 }
 
 const char *Item_ident::full_name() const

sql/item_strfunc.h

@@ -469,7 +469,7 @@ class Item_func_binary :public Item_str_func
    }
   void fix_length_and_dec() 
   { 
-    str_value.set_charset(my_charset_bin); 
+    set_charset(my_charset_bin); 
     max_length=args[0]->max_length; 
   }
   void print(String *str) { print_op(str); }
@@ -485,7 +485,7 @@ class Item_load_file :public Item_str_func
   const char *func_name() const { return "load_file"; }
   void fix_length_and_dec()
   { 
-    str_value.set_charset(my_charset_bin);
+    set_charset(my_charset_bin);
     maybe_null=1; 
     max_length=MAX_BLOB_WIDTH;
   }