Description:
------------
Calling object methods with uppercase I characters in their names fails when the locale is set to Turkish (tr_TR). This is presumably because 'i' is not the lowercase equivalent to 'I' in the language, so strcasecmp("I", "i") returns a non-zero value.

Reproduce code:
---------------
<?php
class C {
    function I() {
        echo "I there!\n";
    }
}
$c = new C;

setlocale(LC_ALL, 'en_AU');
$c->I();

setlocale(LC_ALL, 'tr_TR');
$c->I();
?>

Expected result:
----------------
I there!
I there!

Actual result:
--------------
I there!

Fatal error: Call to undefined method C::I() in /tmp/undefined.php on line 15