Bug#34778435: crashing in Item_field::subst_argument_checker.

Problem: When the ORDER BY clause was pushed down into the
parenthesised query block, we did not move the window function lists
from the outer query block to the inner query block. As a result, the
setup of those window functions was missed during
Query_block::prepare(), and any query expressions inside those window
functions were not prepared. Further optimization of such unprepared
expressions would lead to a crash.

Solution: Move the window function list from the outer query block to
the inner query block.

Change-Id: Ided5303d8ce2b99ae42a1be955356400c0a9d565

Author: mithuncy

sql/query_term.cc

@@ -112,6 +112,7 @@ Query_term *Query_term::pushdown_limit_order_by(Query_term_set_op *parent) {
             child_block->select_limit == nullptr) {
           child_block->order_list = this_block->order_list;
           child_block->absorb_limit_of(this_block);
+          child_block->m_windows.prepend(&this_block->m_windows);
 
           if (this_block->first_inner_query_expression() != nullptr) {
             // Change context of any items in ORDER BY to child block