Enabled the interrupts api to compile

libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX/gpio_irq_api.c

@@ -23,8 +23,9 @@
 
 static uint32_t channel_ids[CHANNEL_NUM] = {0};
 static gpio_irq_handler irq_handler;
-#warning TODO(@toyowata): need implimentation
-#if 0
+
+#warning (matthewelse) This code isn't working yet, so don't rely on it, or try to use it.
+
 static inline void handle_interrupt_in(uint32_t channel) {
     uint32_t ch_bit = (1 << channel);
 
@@ -127,6 +128,4 @@ void gpio_irq_set(gpio_irq_t *obj, gpio_irq_event event, uint32_t enable) {
             &port_reg->IENF &= ~ch_bit;
         }
     }
-}
-
-#endif
+}