PS and SP made compatible in mechanism used for preparing query for rexecutions (Bug #2266)

mysql-test/r/sp.result:
  test suite for Bug #2266
mysql-test/t/sp.test:
  test suite for Bug #2266
sql/item_subselect.cc:
  made ancestor for Statement (Item_arena)
sql/item_subselect.h:
  made ancestor for Statement (Item_arena)
sql/item_sum.cc:
  made ancestor for Statement (Item_arena)
sql/item_sum.h:
  made ancestor for Statement (Item_arena)
sql/mysql_priv.h:
  reset_stmt_for_execute use PS and SP
sql/sp_head.cc:
  sp_head use Item_arena as ancestor to be PS cleunup compatible
  SP use PS storing/restoring/cleanup mechanisms
  cleanup() of SP Items added
  Items created in temporary memory pool during SP execution saved for normal freeing after SP execution
sql/sp_head.h:
  sp_head use Item_arena
sql/sql_base.cc:
  made ancestor for Statement (Item_arena)
  results of wild_setup made permanent
  setup_conds make natural joins expanding only once and store results in PS/SP memory
sql/sql_class.cc:
  made ancestor for Statement (Item_arena)
sql/sql_class.h:
  made ancestor for Statement (Item_arena)
  method to detect PS preparation added
sql/sql_delete.cc:
  storing where for DELETE and mark first execution
sql/sql_derived.cc:
  use method
sql/sql_insert.cc:
  mark first execution for INSERT
sql/sql_lex.cc:
  flags to correctly make transformations of query and storing them in memory of PS/SP
  made ancestor for Statement (Item_arena)
sql/sql_lex.h:
  reved variable od SP ol saving data
  flags to correctly make transformations of query and storing them in memory of PS/SP
sql/sql_parse.cc:
  cleunup unit for any query
sql/sql_prepare.cc:
  made ancestor for Statement (Item_arena)
  storing where moved to preparation
  changed interface of reset_stmt_for_execute to use it is SP
  do not restore where/order by/group by before first execution (but tables and unit can be chenged without execution and should be prepared (subqueries executes on demand))
sql/sql_select.cc:
  storing where for SELECT/multi-DELETE/... and mark first execution
sql/sql_union.cc:
  made ancestor for Statement (Item_arena)
sql/sql_update.cc:
  storing where for UPDATE and mark first execution

sql/sql_class.cc

@@ -86,7 +86,7 @@ extern "C" void free_user_var(user_var_entry *entry)
 ** Thread specific functions
 ****************************************************************************/
 
-THD::THD():user_time(0), current_statement(0), is_fatal_error(0),
+THD::THD():user_time(0), current_arena(0), is_fatal_error(0),
 	   last_insert_id_used(0),
 	   insert_id_used(0), rand_used(0), in_lock_tables(0),
 	   global_read_lock(0), bootstrap(0), spcont(NULL)
@@ -1210,24 +1210,48 @@ int select_dumpvar::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
 }
 
 
-/*
-  Statement functions 
-*/
-
-Statement::Statement(THD *thd)
-  :id(++thd->statement_id_counter),
-  set_query_id(1),
-  allow_sum_func(0),
-  lex(&main_lex),
-  query(0),
-  query_length(0),
-  free_list(0)
+Item_arena::Item_arena(THD* thd)
+  :free_list(0)
 {
   init_sql_alloc(&mem_root,
                  thd->variables.query_alloc_block_size,
                  thd->variables.query_prealloc_size);
 }
 
+
+Item_arena::Item_arena()
+  :free_list(0)
+{
+  bzero((char *) &mem_root, sizeof(mem_root));
+}
+
+
+Item_arena::Item_arena(bool init_mem_root)
+  :free_list(0)
+{
+  if (init_mem_root)
+    bzero((char *) &mem_root, sizeof(mem_root));
+}
+
+
+Item_arena::~Item_arena()
+{}
+
+
+/*
+  Statement functions 
+*/
+
+Statement::Statement(THD *thd)
+  :Item_arena(thd),
+  id(++thd->statement_id_counter),
+  set_query_id(1),
+  allow_sum_func(0),
+  lex(&main_lex),
+  query(0),
+  query_length(0)
+{}
+
 /*
   This constructor is called when statement is a subobject of THD:
   Some variables are initialized in THD::init due to locking problems
@@ -1235,15 +1259,14 @@ Statement::Statement(THD *thd)
 */
 
 Statement::Statement()
-  :id(0),
+  :Item_arena(),
+  id(0),
   set_query_id(1),
   allow_sum_func(0),                            /* initialized later */
   lex(&main_lex),
   query(0),                                     /* these two are set */ 
-  query_length(0),                              /* in alloc_query() */
-  free_list(0)
+  query_length(0)                               /* in alloc_query() */
 {
-  bzero((char *) &mem_root, sizeof(mem_root));
 }
 
 
@@ -1264,14 +1287,14 @@ void Statement::set_statement(Statement *stmt)
 }
 
 
-void Statement::set_n_backup_item_arena(Statement *set, Statement *backup)
+void Item_arena::set_n_backup_item_arena(Item_arena *set, Item_arena *backup)
 {
   backup->set_item_arena(this);
   set_item_arena(set);
 }
 
 
-void Statement::restore_backup_item_arena(Statement *set, Statement *backup)
+void Item_arena::restore_backup_item_arena(Item_arena *set, Item_arena *backup)
 {
   set->set_item_arena(this);
   set_item_arena(backup);
@@ -1279,7 +1302,7 @@ void Statement::restore_backup_item_arena(Statement *set, Statement *backup)
   init_alloc_root(&backup->mem_root, 0, 0);
 }
 
-void Statement::set_item_arena(Statement *set)
+void Item_arena::set_item_arena(Item_arena *set)
 {
   mem_root= set->mem_root;
   free_list= set->free_list;