Revert "Align with namespace change in ESP8266 Arduino implementation of InterruptLock."

Until next release of ESP8266 Arduino, the accompanying fix for the same issue there is not
available to use - undo this revert when time comes.

This reverts commit 65b884a.

Author: dok-net

DHT.h

@@ -23,6 +23,7 @@
   #include <interrupts.h>
  #endif
 
+
 /* Uncomment to enable printing out nice debug messages. */
 //#define DHT_DEBUG
 
@@ -76,9 +77,7 @@ class DHT {
 
 };
 
-#if defined(ESP8266)
-using esp8266::InterruptLock;
-#else
+#if !defined(ESP8266)
 /*! 
  *  @brief  Class that defines Interrupt Lock Avaiability
  */