Use Guard alias and DEV_GUARDED macro in SmartVM.

CodingStandards.txt

@@ -196,7 +196,7 @@ a. Prefer 'using' to 'typedef'. e.g. using ints = std::vector<int>; rather than
 b. Generally avoid shortening a standard form that already includes all important information:
 - e.g. stick to shared_ptr<X> rather than shortening to ptr<X>.
 c. Where there are exceptions to this (due to excessive use and clear meaning), note the change prominently and use it consistently.
-- e.g. using Guard = boost::lock_guard<std::mutex>; ///< Guard is used throughout the codebase since it's clear in meaning and used commonly. 
+- e.g. using Guard = std::lock_guard<std::mutex>; ///< Guard is used throughout the codebase since it's clear in meaning and used commonly. 
 d. In general expressions should be roughly as important/semantically meaningful as the space they occupy.
 
 
@@ -226,4 +226,3 @@ a. Includes should go in order of lower level (STL -> boost -> libdevcore -> lib
 #include <libethereum/Defaults.h>
 
 b. The only exception to the above rule is the top of a .cpp file where its corresponding header should be located.
-

libevm/SmartVM.cpp

@@ -26,6 +26,7 @@
 #include <queue>
 #include <libdevcore/Log.h>
 #include <libdevcore/SHA3.h>
+#include <libdevcore/Guards.h>
 #include <evmjit/JIT.h>
 #include <evmjit/libevmjit-cpp/Utils.h>
 #include "VMFactory.h"
@@ -92,20 +93,16 @@ namespace
 
 		~JitWorker()
 		{
-			{
-				std::lock_guard<std::mutex> lock{x_mutex};
+			DEV_GUARDED(x_mutex)
 				m_finished = true;
-			}
 			m_cv.notify_one();
 			m_worker.join();
 		}
 
 		void push(JitTask&& _task)
 		{
-			{
-		        std::lock_guard<std::mutex> lock(x_mutex);
-		        m_queue.push(std::move(_task));
-		    }
+			DEV_GUARDED(x_mutex)
+				m_queue.push(std::move(_task));
 			m_cv.notify_one();
 		}
 	};