* Csv Handling of Booleans (and an 8.1 Deprecation)
PhpSpreadsheet writes boolean values to a Csv as null-string/1, and treats input values of 'true' and 'false' as if they were strings. On the other hand, Excel writes boolean values to a Csv as TRUE/FALSE, and case-insensitively treats a matching string as boolean on read. This PR changes PhpSpreadsheet to match Excel.
A side-effect of this change is that it fixes behavior incorrectly reported as a bug in PR #2048. That issue was closed, correctly, as user error. The user had altered Csv Writer, including adding ```declare(strict_types=1);```; that declaration was the cause of the error. The "offending" statements, calls to strpbrk and str_replace, will now work correctly whether or not strict_types is in use.
And, just as I was getting ready to push this, the dailies for PHP 8.1 introduced a change deprecating auto_detect_line_endings. Csv Reader uses that setting; it allows it to process a Csv with Mac line endings, which happens to be something that Excel can do. As they say in https://wiki.php.net/rfc/deprecations_php_8_1, where the proposal passed without a single dissenting vote, "These newlines were used by “Classic” Mac OS, a system which has been discontinued in 2001, nearly two decades ago. Interoperability with such systems is no longer relevant." I tend to agree, but I don't know that we're ready to pull the plug yet. I don't see an easy way to emulate that functionality. For now, I have silenced the deprecation notices with at signs. I have also added a test case which will fail when support for that setting is pulled; this will give time to consider alternatives.
* Scrutinizer: Handling ini_set
This could be interesting. It doesn't like not handling an error condition for ini_set. Let's see if this satisfies it.
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