The problem was then when a column reference was resolved to a view column, the new Item
created for this column contained the name of the view, and not the view alias.


mysql-test/r/view.result:
  Additional test for BUG#13410.
mysql-test/t/view.test:
  Additional test for BUG#13410.
sql/item.cc:
  Correctly cast 'cur_field' to Item_ident because if the original item is
  an Item_field, the cur_field is either an Item_field or an Item_ref.
  Thus we have to cast cur_field to a common super-class of both.
sql/item.h:
  - real_item() may be called before Item_ref::ref is set
    (i.e. the Item_ref object was resolved).
  - To avoid a crash and to return some meaningful value
    in such cases we return 'this'.
sql/sql_base.cc:
  - 'item' may be an Item_ref, so we test for the type of the actual
    referenced item.
  - Correctly cast 'cur_field' to Item_ident because if the original
    item is an Item_field, the cur_field is either an Item_field or an
    Item_ref. Thus we have to cast cur_field to a common super-class
    of both.
sql/table.cc:
  - When creating a new Item for a reference to a view column, use the view alias,
    and not the real view name.
  - Removed old code