Expand description
FFI bindings to ARPACK-NG.
The bindings are pre-generated by bindgen against <arpack/arpack.h>
from ARPACK-NG (the _c C-callable wrappers introduced in 3.8.0).
Linking is handled by build.rs via pkg-config.
No safety wrappers live here — see the sibling arpack crate for the
safe Rust API.