The function test_if_skip_sort_order ignored any covering index used for ref
access of a table in a query with ORDER BY if this index was incompatible 
with the ORDER BY list and there was another covering index compatible with
this list. 
As a result sub-optimal execution plans were chosen for some queries with
ORDER BY clause. 


mysql-test/r/distinct.result:
  Adjusted results after the fix for bug#35844.
mysql-test/r/order_by.result:
  Added a test case for bug#35844.
mysql-test/t/order_by.test:
  Added a test case for bug#35844.