Rename ssl_set_bio_timeout() to set_bio()

Initially thought it was best to keep the old function around and add a new
one, but this so many ssl_set_xxx() functions are changing anyway...

programs/ssl/dtls_server.c

@@ -279,7 +279,7 @@ reset:
         goto exit;
     }
 
-    mbedtls_ssl_set_bio_timeout( &ssl, &client_fd,
+    mbedtls_ssl_set_bio( &ssl, &client_fd,
                          mbedtls_net_send, mbedtls_net_recv, mbedtls_net_recv_timeout );
 
     printf( " ok\n" );