igbinary extension

Igbinary is a drop in replacement for the standard php serializer. Instead of
the time and space consuming textual representation used by PHP's serialize(), igbinary stores php data
structures in a compact binary form. Savings are significant when using
memcached or similar memory based storages for serialized data.

* Reduce excessive inlining to reduce shared library size.
* Miscellaneous optimizations.
* Update test expectations to handle changes to var_export output (fully qualified class names) in PHP 8.2.
* Throw an Error when igbinary_unserialize would add dynamic properties to class definitions that forbid them in PHP 8.0+
(especially PHP 8.2 `readonly` classes)
* Emit a deprecation notice when igbinary_unserialize() adds dynamic properties to a class without `#[AllowDynamicProperties]` in PHP 8.2.
Doing that would become an Error in PHP 9.0.
* Set up CI job to build dlls on https://github.com/igbinary/igbinary - at the moment, the infrastructure used by the Windows for php team has been broken for months.