The test case for the bug#31048 checks that there is no crash on stack
overrun. But due to different stack sizes on different platforms it failed
on some of them.

The new test case check that a query with at least 4 level subquery nesting
works without the stack overrun nesting and other levels of nesting doesn't
cause a crash.


mysql-test/t/subselect.test:
  Corrected test case for the bug#31048.
mysql-test/r/subselect.result:
  Corrected test case for the bug#31048.