use C++11 static variables as memory barrier

modules/core/src/precomp.hpp

@@ -364,15 +364,8 @@ bool __termination;  // skip some cleanups, because process is terminating
 
 cv::Mutex& getInitializationMutex();
 
-// TODO Memory barriers?
 #define CV_SINGLETON_LAZY_INIT_(TYPE, INITIALIZER, RET_VALUE) \
-    static TYPE* volatile instance = NULL; \
-    if (instance == NULL) \
-    { \
-        cv::AutoLock lock(cv::getInitializationMutex()); \
-        if (instance == NULL) \
-            instance = INITIALIZER; \
-    } \
+    static TYPE* const instance = INITIALIZER; \
     return RET_VALUE;
 
 #define CV_SINGLETON_LAZY_INIT(TYPE, INITIALIZER) CV_SINGLETON_LAZY_INIT_(TYPE, INITIALIZER, instance)