ruby: move towards more modern RTypedData

Virtually the whole ruby core moved from RData to RTypeData, let's do so
ourselves too.

Basically the information typically passed through Data_Wrap_Struct is
now stored in a struct rb_data_type_t (mark and free functions). This
has the advantage that more information can be easily added, like the
name of the type, a custom data ponter, and more.

Data_Wrap_Struct is replaced with TypedData_Wrap_Struct, and the
information is stored in a struct rb_data_type_t, rather than passed
as arguments.

Check_Type is replaced with Check_TypedStruct, which is a wrapper for
rb_check_typeddata (with casts).

        #define Check_TypedStruct(v, t)      \
            rb_check_typeddata(RBIMPL_CAST((VALUE)(v)), (t))

We can use rb_check_typeddata directly, just like we use rb_data_object_get
directly.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>