fixed memory leacks


mysql-test/r/subselect.result:
  some changes in subselect tests
mysql-test/t/subselect.test:
  some changes in subselect tests
sql/item.cc:
  some item made copyable
  methods for creating copy of item list
  tmp_table_field() splited
sql/item.h:
  some item made copyable
  methods for creating copy of item list
  tmp_table_field() splited
sql/item_cmpfunc.cc:
  changed references creation
sql/item_cmpfunc.h:
  changed references creation
sql/item_func.cc:
  some item made copyable
  methods for creating copy of item list
  changed references creation
sql/item_func.h:
  some item made copyable
  methods for creating copy of item list
  changed references creation
  tmp_table_field() splited
sql/item_subselect.cc:
  changed references creation
sql/item_sum.cc:
  some item made copyable
  methods for creating copy of item list
sql/item_sum.h:
  some item made copyable
  methods for creating copy of item list
sql/item_timefunc.h:
  tmp_table_field() splited
sql/item_uniq.h:
  some item made copyable
  methods for creating copy of item list
sql/mysql_priv.h:
  fixed subselects with temporary tables
sql/sql_base.cc:
  fixed subselects with temporary tables
sql/sql_class.h:
  fixed subselects with temporary tables
sql/sql_delete.cc:
  fixed subselects with temporary tables
sql/sql_derived.cc:
  fixed subselects with temporary tables
sql/sql_do.cc:
  fixed subselects with temporary tables
sql/sql_insert.cc:
  fixed subselects with temporary tables
sql/sql_lex.cc:
  fixed subselects with temporary tables
sql/sql_lex.h:
  fixed subselects with temporary tables
sql/sql_list.h:
  fixed subselects with temporary tables
sql/sql_load.cc:
  fixed subselects with temporary tables
sql/sql_olap.cc:
  fixed subselects with temporary tables
sql/sql_parse.cc:
  fixed subselects with temporary tables
sql/sql_prepare.cc:
  fixed subselects with temporary tables
sql/sql_select.cc:
  fixed subselects with temporary tables
sql/sql_select.h:
  fixed subselects with temporary tables
sql/sql_table.cc:
  fixed subselects with temporary tables
sql/sql_union.cc:
  fixed subselects with temporary tables
sql/sql_update.cc:
  fixed subselects with temporary tables
sql/sql_yacc.yy:
  fixed subselects with temporary tables