The bug report has demonstrated the following two problems.
1. If an ORDER/GROUP BY list includes a constant expression being 
optimized away and, at the same time, containing single-row
subselects that return more that one row, no error is reported.
Strictly speaking the standard allows to ignore error in this case.
Yet, now a corresponding fatal error is reported in this case.
2. If a query requires sorting by expressions containing single-row
subselects that, however, return more than one row, then the execution
of the query may cause a server crash. 
To fix this some code has been added that blocks execution of a subselect
item in case of a fatal error in the method Item_subselect::exec.


mysql-test/r/subselect.result:
  Added a test cases for bug #24653.
mysql-test/t/subselect.test:
  Added a test cases for bug #24653.
sql/filesort.cc:
  Fixed bug #24653.
  Added a check for fatal error after reading the next row from the table
  in the function find_all_keys.
sql/item.cc:
  Fixed bug #24653.
  Down-ported calculation of the attribute with_subselect of for Item objects.
sql/item.h:
  Fixed bug #24653.
  Down-ported calculation of the attribute with_subselect of for Item objects.
sql/item_cmpfunc.cc:
  Fixed bug #24653.
  Down-ported calculation of the attribute with_subselect of for Item objects.
sql/item_cmpfunc.h:
  Fixed bug #24653.
  Down-ported calculation of the attribute with_subselect of for Item objects.
sql/item_func.cc:
  Fixed bug #24653.
  Down-ported calculation of the attribute with_subselect of for Item objects.
sql/item_subselect.cc:
  Fixed bug #24653.
  Added a check for fatal error in the method Item_subselect::exec
  to block evaluation of subselects in erroneous situations.
  Down-ported calculation of the attribute with_subselect of for Item objects.
sql/sql_select.cc:
  Fixed bug #24653.
  Added a check to verify that any constant expression used
  in ORDER BY and/or GROUP BY lists which is optimized away
  does not contain subselects returning more than one row.
  If it does a fatal error is reported.