Fix missing apm3_io_led_init

apm3hook/apm3hook.def

@@ -15,6 +15,7 @@ EXPORTS
     apm3_io_get_opbtns
     apm3_io_init
     apm3_io_poll
+    apm3_io_led_init
     CFW_init
     CFW_term
     CFW_open

apm3io/apm3io.c

@@ -52,3 +52,8 @@ void apm3_io_get_opbtns(uint8_t *opbtn)
         *opbtn = apm3_opbtn;
     }
 }
+
+HRESULT apm3_io_led_init(void)
+{
+    return S_OK;
+}

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);