* Rough implementation of struct properties
* Store properties hashtable once
* Tidy up handler functions with exceptions
* Add stub `get_properties` function for codegen structs
* Remove nightly features
* Revert storing properties
Technically, the zend object _could_ move in memory, leaving dangling
references in the properties hashtable. We will just build the hashtable
when required.
* Added `#[prop]` attribute
* Add pointer type to zval, tidy up zend string
* Add support for method properties
* Add `#[getter]` and `#[setter]` attributes
* Update documentation with method properties
* Tidy up macros code
* Remove string gc checks (done on PHP side)
* Move `RegisteredClass` implementation to module, update docs
* Fix read property `rv` segfault
* Fixed doctests
