*: fix SO_BINDTODEVICE. Kernel wants at least IFNAMSIZ bytes there.

include/libbb.h

@@ -437,6 +437,7 @@ ssize_t xsendto(int s, const void *buf, size_t len, const struct sockaddr *to,
  * Turn it on before you call bind(). */
 void setsockopt_reuseaddr(int fd) FAST_FUNC; /* On Linux this never fails. */
 int setsockopt_broadcast(int fd) FAST_FUNC;
+int setsockopt_bindtodevice(int fd, const char *iface) FAST_FUNC;
 /* NB: returns port in host byte order */
 unsigned bb_lookup_port(const char *port, const char *protocol, unsigned default_port) FAST_FUNC;
 typedef struct len_and_sockaddr {