Add basic structures for netinet/in.h crate

Cargo.lock

Cargo.toml

src/lib.rs

src/netinet/Cargo.toml

src/netinet/in/Cargo.toml

src/netinet/in/build.rs

src/netinet/in/cbindgen.toml

src/netinet/in/src/lib.rs

src/netinet/src/lib.rs