sql/item.cc:
  Fixed Item usual constructor to call current_thd only once.
  Fixed copy constructor to receive THD pointer via arguments.
  added comments
  removed counter-1 and unnessesary initializaton of counter
sql/item.h:
  Fixed copy constructor to receive THD pointer via arguments.
  Renamed get_same to copy_or_same.
  THD pointetr added to copy_or_same and get_tmp_table_item.
sql/item_cmpfunc.cc:
  fixed layout
  fixed direct call of destructor
sql/item_func.cc:
  fiex layout
  THD pointetr added to get_tmp_table_item.
sql/item_func.h:
  THD pointetr added to get_tmp_table_item.
sql/item_sum.cc:
  Fixed copy constructor to receive THD pointer via arguments.
  Renamed get_same to copy_or_same.
  THD pointetr added to copy_or_same and get_tmp_table_item.
sql/item_sum.h:
  fixed layout
  Fixed copy constructor to receive THD pointer via arguments.
  Renamed get_same to copy_or_same.
  THD pointetr added to copy_or_same and get_tmp_table_item.
sql/item_uniq.h:
  Fixed copy constructor to receive THD pointer via arguments.
  Renamed get_same to copy_or_same.
  THD pointetr added to copy_or_same and get_tmp_table_item.
sql/sql_base.cc:
  count from 0
sql/sql_select.cc:
  removed counter-1 and unnessesary initializaton of counter
  THD pointetr added to get_tmp_table_item and change_to_use_tmp_fields.