[php-src] Issue #18897: printf: empty precision is interpreted as precision 6, not as precision 0

Issue: https://github.com/php/php-src/issues/18897 Author: bhaible ### Description The following code: ```php <?php printf("%.f\n", 3.1415926535); printf("%.0f\n", 3.1415926535); printf("%.6f\n", 3.1415926535); ?> ``` Resulted in this output: ``` 3.141593 3 3.141593 ``` But I expected this output instead: ``` 3 3 3.141593 ``` because the documentation (https://www.php.net/manual/en/function.printf.php and https://www.php.net/manual/en/function.sprintf.php) says "Note: If the period is specified without an explicit value for precision, 0 is assumed." ### PHP Version ```plain PHP 8.3.6 (cli) (built: Mar 19 2025 10:08:38) (NTS) Copyright (c) The PHP Group Zend Engine v4.3.6, Copyright (c) Zend Technologies with Zend OPcache v8.3.6, Copyright (c), by Zend Technologies ``` ### Operating System _No response_