memory leacks in PS with subqueries fixed (adddition to fix of BUG#2462)

sql/item.h:
  mechanism to keep reference in cache array for row IN
sql/item_cmpfunc.cc:
  mechanism to keep reference in cache array for row IN
  layout fixed
sql/item_cmpfunc.h:
  mechanism to keep reference in cache array for row IN
sql/item_subselect.cc:
  fixed memory pools swapping
  prevented deleting Item_in_optimizer cache in case of row IN subquery
sql/mysql_priv.h:
  declarations of function moved to be useful in sql_class.h
sql/sql_base.cc:
  keep fields expanded from '*' in statement memory pool
sql/sql_class.cc:
  fixed restoring/backup of memory pool and list of items
sql/sql_class.h:
  memory allocation methods moved to Statement
  memory pool substituting for preparing
sql/sql_lex.cc:
  ref_pointer_array kept in statement memory
sql/sql_lex.h:
  reinitialization of UNIT
sql/sql_prepare.cc:
  memory allocation/swapping fixed
tests/client_test.c:
  layout fixed

1 files changed, 10 insertions, 4 deletions

diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index cfbf0385b6f..21d4949ad91 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1244,22 +1244,28 @@ void Statement::set_statement(Statement *stmt)
   mem_root=       stmt->mem_root;
 }
 
+
 void Statement::set_n_backup_item_arena(Statement *set, Statement *backup)
 {
-  backup->mem_root= mem_root;
-  backup->free_list= free_list;
+  backup->set_item_arena(this);
   set_item_arena(set);
 }
 
 
+void Statement::restore_backup_item_arena(Statement *set, Statement *backup)
+{
+  set->set_item_arena(this);
+  set_item_arena(backup);
+  // reset backup mem_root to avoid its freeing
+  init_alloc_root(&backup->mem_root, 0, 0);
+}
+
 void Statement::set_item_arena(Statement *set)
 {
   mem_root= set->mem_root;
   free_list= set->free_list;
 }
 
-
-
 Statement::~Statement()
 {
   free_root(&mem_root, MYF(0));