ffi/Hostent: ignore unused variable error on addr_type

We don't really use it for now, this is already encoded in the
addrlist. But let's keep this structure aligned with the glibc
counterpart.

src/ffi.rs

@@ -98,6 +98,7 @@ mod glibcffi {
 pub struct Hostent {
     pub name: CString,
     pub aliases: Vec<CString>,
+    #[allow(dead_code)]
     pub addr_type: i32,
     pub addr_list: Vec<std::net::IpAddr>,
     pub herrno: i32,