fixes the bitrig d_namlen compile error

Author: Dave Huseby

src/unix/bsd/openbsdlike/bitrig.rs

@@ -17,7 +17,7 @@ s! {
         pub d_off: ::off_t,
         pub d_reclen: u16,
         pub d_type: u8,
-        pub d_namelen: u8,
+        pub d_namlen: u8,
         __d_padding: [u8; 4],
         pub d_name: [::c_char; 256],
     }