fixes ifindex/2 to return correct interface index

[GoelDeepak]

@msantos Could you please take a look?

[msantos]

Hey @GoelDeepak ! Looks good! It seems if_index is now an unsigned 32-bit integer (assuming it was 8-bits before and that wasn't a mistake :):

struct if_nameindex
  {
    unsigned int if_index;  /* 1, 2, ... */
    char *if_name;      /* null terminated name: "eth0", ... */
  };

Thanks so much for the patch!