itself when executing queries referring to a view with GROUP BY
an expression containing non-constant interval.
It happened because Item_date_add_interval::eq neglected the
fact that the method can be applied to an expression of the form
    date(col) + interval time_to_sec(col) second
at the time when col could not be evaluated yet.
An attempt to evaluate time_to_sec(col) in this method resulted
in a crash.


mysql-test/r/view.result:
  Added a test case for bug #19490.
mysql-test/t/view.test:
  Added a test case for bug #19490.
sql/item_timefunc.cc:
  Fixed bug #19490. The bug that caused server crash manifested
  itself when executing queries referring to a view with GROUP BY
  an expression containing non-constant interval.
  It happened because Item_date_add_interval::eq neglected the
  fact that the method can be applied to an expression of the form
      date(col) + interval time_to_sec(col) second
  at the time when col could not be evaluated yet.
  An attempt to evaluate time_to_sec(col) in this method resulted
  in a crash.
  The code of Item_date_add_interval::eq was corrected.