PHP 8 update, use zend_objects or zval depending upon version

[msaladna]

PHP 8 changes Object Handlers API to receive zend_object* instead of zval*. Compilation is preserved against 7.x. properties can be retrieved with zend_std_get_properties() for refcounting.

Still looking into the memory leaks as noted in #12. This extension compiles and runs cleanly against 8 now 👯

[stefansaraev]

thanks @msaladna

I had some random segfaults, fixed with your PR now. I owe you (and Derick!) a 🍺 :)