Description:
------------
According to line 473, the second parameter of IntlChar::forDigit() should be optional and default to 10.  However, PHP is requiring that I provide a value for this second parameter.

Test script:
---------------
See https://3v4l.org/sOcGh or run this yourself:

<?php
var_dump(IntlChar::forDigit(0));
var_dump(IntlChar::forDigit(3));
var_dump(IntlChar::forDigit(3, 10));
var_dump(IntlChar::forDigit(10));
var_dump(IntlChar::forDigit(10, 16));
?>

Expected result:
----------------
int(48)
int(51)
int(51)
int(0)
int(97)

Actual result:
--------------
Warning: IntlChar::forDigit() expects exactly 2 parameters, 1 given in /in/sOcGh on line 2
NULL

Warning: IntlChar::forDigit() expects exactly 2 parameters, 1 given in /in/sOcGh on line 3
NULL
int(51)

Warning: IntlChar::forDigit() expects exactly 2 parameters, 1 given in /in/sOcGh on line 5
NULL
int(97)