Fix missing apm3_io_led_init

apm3io/apm3io.h

@@ -42,3 +42,14 @@ HRESULT apm3_io_poll(void);
    Minimum API version: 0x0100 */
 
 void apm3_io_get_opbtns(uint8_t *opbtn);
+
+/* Initialize LED emulation. This function will be called before any
+   other apm3_io_led_*() function calls.
+
+   All subsequent calls may originate from arbitrary threads and some may
+   overlap with each other. Ensuring synchronization inside your IO DLL is
+   your responsibility. 
+   
+   Minimum API version: 0x0101 */
+
+HRESULT apm3_io_led_init(void);