mysql-test/r/subselect.result:
  test suite for BUG#2838
mysql-test/t/subselect.test:
  test suite for BUG#2838
sql/item.cc:
  revision of fix_fields() calls
  removed unnecessary variabl, and used correct last parameter of fix_fields()
sql/item_cmpfunc.cc:
  revision of fix_fields() calls (BUG#2838)
sql/item_func.cc:
  revision of fix_fields() calls
sql/item_row.cc:
  changed for efficience (and to be similar for Item_func::fix_fields)
sql/item_subselect.cc:
  fixed last arguments for fix_fields call
sql/item_sum.cc:
  layout fixed
  revision of fix_fields() calls
sql/log_event.cc:
  revision of fix_fields() calls
sql/set_var.cc:
  revision of fix_fields() calls
sql/sql_base.cc:
  revision of fix_fields() calls
sql/sql_class.cc:
  revision of fix_fields() calls
sql/sql_handler.cc:
  revision of fix_fields() calls