Add missing cstddef include for C++ builds

[cmb69]

I've noticed this while trying to build sqlsrv (a C++ extension) for PHP 8.4.0alpha2 with Visual Studio 2022. While my C++ knowledge is rather limited, I think this is the proper way to make max_align_t available. At least, MSVC wouldn't know it without the include, and error out.

@arnaud-lb, since you've written that code, could you please have look?

[arnaud-lb]

Thank you! LGTM!

[macintoshplus]

@cmb69, this fix is no longer necessary to build sqlsrv?

[cmb69]

No, the fix is necessary (possibly for other packages, too), therefore it has been applied ("cmb69 closed this in ab449a7" means it has been applied; this alternative to merging is not uncommon when adding a NEWS entry, for instance).

[macintoshplus]

Thank you. I understand. This is a confusing way of doing things for me.

[cmb69]

This is a confusing way of doing things for me.

This is because GH expects to merge everything into the development branch and to cherry-pick from there to applicable release branches, but php-src wants to apply to the lowest applicable release branch, and to merge up from there. While the latter is still possible by merging via GH GUI (even to release branches), unfortunate conflicts may occur due to simultaneous merges, and the history ("git tree") might be harder to follow.

[Jan-E]

And some of those fixes are backported even further: https://github.com/remicollet/php-src-security/commits/PHP-8.0-security-backports/