Bug#19136: Manual 5.0->5.1 merge

sql/item_func.cc:
  Auto merged
sql/sql_select.cc:
  Auto merged

mysql-test/r/rpl_user_variables.result

@@ -78,5 +78,6 @@ abcn1
 abcn1n2
 abc\def
 This is a test
+insert into t1 select * FROM (select @var1 union  select @var2) AS t2;
 drop table t1;
 stop slave;