[php-src] Issue #21210: parse_ini_string() fails on "(" character in comment

Issue: https://github.com/php/php-src/issues/21210
Author: tstoeckler

### Description

The following code:

```php
<?php
print_r(parse_ini_string("# a comment (with parens)\nkey=value\n"));
```

Resulted in this output:
```
PHP Warning:  syntax error, unexpected '(' in Unknown on line 1
 in Command line code on line 1
```

But I expected this output instead:
```
Array
(
    [key] => value
)
```

in particular because it is the output of
```php
<?php
print_r(parse_ini_string("# a comment\nkey=value\n"));
```


### PHP Version

```plain
PHP 8.5.0 (cli) (built: Nov 18 2025 08:02:20) (NTS gcc x86_64)
Copyright (c) The PHP Group
Built by Remi's RPM repository <https://rpms.remirepo.net/> #StandWithUkraine
Zend Engine v4.5.0, Copyright (c) Zend Technologies
    with Xdebug v3.5.0, Copyright (c) 2002-2025, by Derick Rethans
    with Zend OPcache v8.5.0, Copyright (c), by Zend Technologies

(Also tested with PHP 8.4 with the same result)
```

### Operating System

Fedora Linux 43