Fixed bug #11412.
  Reversed the patch of cs 1.1934 for the function 
  create_tmp_table. Modified the function to support
  tem_ref objects created for view fields.
item_buff.cc:
  Fixed bug #11412.
  Modified implementation of new_Cached_item to support
  cacheing of view fields.
item.h:
  Fixed bug #11412.
  Changed implementation of Item_ref::get_tmp_table_field and
  added Item_ref::get_tmp_table_item to support Item_ref objects
  created for view fields.
view.test, view.result:
  Added a test case for bug #11412.