Avoid compiler warning because of unused variable.

core/net/ip/uip-nameserver.c

@@ -57,7 +57,9 @@ typedef struct uip_nameserver_record {
 } uip_nameserver_record;
 
 /** \brief Initialization flag */
+#if UIP_NAMESERVER_POOL_SIZE > 1
 static uint8_t initialized = 0;
+#endif
 
 /** \name List and memory block
  * @{