Ensure that references in typed properties have their property type info added to the reference group

See php-src ext/standard/var_unserializer.re

Fix any bugs
- And add unit tests that after igbinary_unserialize sets a typed property to a reference, the reference can't be set to incompatible types later (e.g. by the caller)
- Add unit tests that igbinary_unserialize throws if the reference type is incompatible