Merge pull request #336 from jaecktec/master

Enable ESP32 to use PubSubClient (make MQTT_CALLBACK_SIGNATURE functional)

Author: knolleary

README.md

@@ -37,6 +37,7 @@ boards and shields, including:
  - TI CC3000 WiFi - [library](https://github.com/sparkfun/SFE_CC3000_Library)
  - Intel Galileo/Edison
  - ESP8266
+ - ESP32
 
 The library cannot currently be used with hardware based on the ENC28J60 chip –
 such as the Nanode or the Nuelectronics Ethernet Shield. For those, there is an

src/PubSubClient.h

@@ -76,7 +76,7 @@
 // Maximum size of fixed header and variable length size header
 #define MQTT_MAX_HEADER_SIZE 5
 
-#ifdef ESP8266
+#if defined(ESP8266) || defined(ESP32)
 #include <functional>
 #define MQTT_CALLBACK_SIGNATURE std::function<void(char*, uint8_t*, unsigned int)> callback
 #else