Description:
------------
Attempting to instantiate a class that:

- extends IntlCalendar or IntlGregorianCalendar; AND
- adds a property

will result in a segfault under PHP 7.

See https://3v4l.org/r3eDR

Test script:
---------------
class A extends IntlCalendar {
    public function __construct() {}
    private $a;
}
var_dump(new A());

Expected result:
----------------
object(A)#1 (1) {
  ["valid"]=>
  bool(false)
}

Actual result:
--------------
(Process exited with code 139.)