Description:
------------
Using [] in a key name can result in a crash if the corresponding setting was previously set to a scalar value.

Reproduce code:
---------------
// Not relevant to the bug
$file = tempnam('./', '');
file_put_contents($file, '
foo  =1;
foo[]=1;
');

// Will make PHP crash
parse_ini_file($file);


Expected result:
----------------
In the attached reproduce code we create a ini file which has 2 keys, "foo" and "foo[]" then we execute parse_ini_file() on the newly-created file.

Because "Characters {}|&~![()" must not be used anywhere in the key" (dixit the manual) I'd expect an error message, or at least a Strict notice.

Actual result:
--------------
PHP segfaults/crashes

(tested on 5.2.1 on WinXP and 5.1.2 on Ubuntu 6.06)