Change CAPI data wrappers

[BuonOmo]

Data_Wrap_Struct has been deprecated a long time ago, we want to replace it with the Typed.. macros.

This refacto should only make the code simpler and will be part of a major with breaking changes, feel free to change the structure (and discuss the changes here beforehand if you are unsure).

See https://github.com/ruby/ruby/blob/HEAD/doc/extension.rdoc