Fail configure for libxml 2 >= 2.13.0

[cmb69]

While we should not make changes to a security branch to support new libxml2 versions, we should at least fail early to avoid confusion; see GH-16863.

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Note that this is not supposed to be merged up, since the compatibility issues has been resolved for PHP-8.2.

cc @nielsdos

[nielsdos]

I agree with the idea, but:

1. perhaps the compatibility fix should be backported anyway given that our macOS CI fails with this PR's approach.
2. we already know that Alpine builds PHP 8.1 with old libxml, so suddenly configuration will fail for them, they'd have to patch this out. Similar situations may cause confusion for other distributors.

[cmb69]

1. perhaps it should be backported anyway given that our macOS CI fails now.

I still don't think it is a good idea to use Homebrew for security branches; it may not even be the best option for stable branches, because they appear to be pretty aggressive with their updates. If you are reasonably sure that backporting 67259e4 is okay, I'm fine with that (not my decision anyway, though). But I expect further issues within the next year (besides that #16789 will not help as of May).

2. we already know that Alpine builds PHP 8.1 with old libxml, so suddenly configuration will fail for them, they'd have to patch this out. Similar situations may cause confusion for other distributors.

Fair point. (I assume you meant "new libxml" instead of "old libxml".)

I guess release managers should decide what we do. @patrickallaert, @ramsey, thoughts?