Align with namespace change in ESP8266 Arduino implementation of InterruptLock.

Author: dok-net

DHT.h

@@ -77,7 +77,9 @@ class DHT {
 
 };
 
-#if !defined(ESP8266)
+#if defined(ESP8266)
+using esp8266::InterruptLock;
+#else
  *  @brief  Class that defines Interrupt Lock Avaiability
  */
 class InterruptLock {