Add some function to wifi class

Some functions are missing but can be added in ESP8266WiFiClass, but to
avoid to update main class, at each release as it is not implemented -
move them to wifi class

esp8266/wifi.h

@@ -21,13 +21,18 @@
 #ifndef WIFI_h
 #define WIFI_h
 #include <Arduino.h>
+#include "IPAddress.h"
+#include <ESP8266WiFi.h>
 
 class WIFI_CONFIG
 {
   public:
   bool Setup();
+  char * mac2str(uint8_t mac [WL_MAC_ADDR_LENGTH]);
+  void configAP(IPAddress local_ip, IPAddress gateway, IPAddress subnet);
   private:
   byte split_ip (char * ptr,byte * part);
+
 };
 
 extern WIFI_CONFIG wifi_config;