Bug#46051: Incorrectly market field caused wrong result.

When during the optimization an item is moved to the upper select
the item's context left unchanged. This caused wrong result in the 
PS/SP mode.
The Item_ident::remove_dependence_processor now sets the context
of the select to which the item is moved to.

mysql-test/r/subselect.result

@@ -4472,10 +4472,6 @@ int_nokey	int_key
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	C	ALL	NULL	NULL	NULL	NULL	20	Using where
-Warnings:
-Note	1276	Field or reference 'test.C.int_nokey' of SELECT #2 was resolved in SELECT #1
-Note	1249	Select 2 was reduced during optimization
-Note	1003	select `test`.`C`.`int_nokey` AS `int_nokey`,`test`.`C`.`int_key` AS `int_key` from `test`.`C` where (`test`.`C`.`int_nokey` = `test`.`C`.`int_key`)
 DROP TABLE C;
 # End of test for bug#45061.
 End of 5.0 tests.

mysql-test/t/subselect.test

@@ -3441,8 +3441,10 @@ INSERT INTO `C` VALUES (9,9), (0,0), (8,6), (3,6), (7,6), (0,4),
 (1,7), (9,4), (0,8), (9,4), (0,7), (5,5), (0,0), (8,5), (8,7),
 (5,2), (1,8), (7,0), (0,9), (9,5);
 
+--disable_warnings
 SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
 EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
+--enable_warnings
 
 DROP TABLE C;
 --echo # End of test for bug#45061.

sql/item.cc

@@ -598,6 +598,7 @@ bool Item_ident::remove_dependence_processor(byte * arg)
   DBUG_ENTER("Item_ident::remove_dependence_processor");
   if (depended_from == (st_select_lex *) arg)
     depended_from= 0;
+  context= &((st_select_lex *) arg)->context;
   DBUG_RETURN(0);
 }