Update bindings

[yutannihilation]

to reflect these changes:

• Use rust constants and rust types in bindgen #160
• Remove VECTOR_PTR from bindings #165

[Ilia-Kosenkov]

Do you know why it switched from c_uint to u32?

[yutannihilation]

Because of this change. #160

[CGMossa]

Maybe due to this https://github.com/extendr/libR-sys/blob/master/build.rs#L460

[yutannihilation]

Thanks for approving!