Add OpenBSD amd64 bindings

[klemensn]

Generated on OpenBSD/amd64 7.0 with

pkg_add rust # cargo and rustc

# pkg_add rust-rustfmt  # used by bindgen
# pkg_add llvm  # required by bindgen
$ cargo install bindgen
$ rustc ./generate-bindings.rs
$ PATH=~/.cargo/bin:/usr/local/bin  # bindgen and rustfmt
$ LIBCLANG_PATH=/usr/local/lib      # for bindgen
$ ./generate-bindings