Update to new TypedData system

[v0dro]

The latest Ruby updates the traditional Data_* macros into TypeData_* macros for creating Ruby objects from C extensions. This allows for more sophisticated typedata management at the C level. The old system will be deprecated soon and we should upgrade.

Here's the docs: https://github.com/ruby/ruby/blob/trunk/doc/extension.rdoc#encapsulate-c-data-into-a-ruby-object

[translunar]

Presumably this is not backwards compatible, right? So we should probably do some kind of #ifdef?

[v0dro]

Yep.