make it work on Windows

Utility/ChangeLog

+
+2018-03-16 Lynn Garren <garren@fnal.gov> 
+
+* Utility/use_atomic.h, Utility/atomic_int.h: 
+  Windows does not recognize the __cplusplus check
+
 ==============================
 15.03.18 Release CLHEP-2.4.0.3
 ==============================

Utility/Utility/atomic_int.h

@@ -8,17 +8,22 @@
 // on macOS, atomic is available starting with Sierra (Darwin 16)
 // ======================================================================
 
-#if __cplusplus >= 201103L
+#if USING_VISUAL
+    #include <atomic>
+    #define CLHEP_ATOMIC_INT_TYPE std::atomic<int>
+#else
+  #if __cplusplus >= 201103L
 
-  #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 7) || __clang__ || USING_VISUAL
+  #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 7) || __clang__
     #include <atomic>
     #define CLHEP_ATOMIC_INT_TYPE std::atomic<int>
   #else
     #define CLHEP_ATOMIC_INT_TYPE int
   #endif
 
-#else
-  #define CLHEP_ATOMIC_INT_TYPE int
+  #else
+    #define CLHEP_ATOMIC_INT_TYPE int
+  #endif
 #endif
 
 #endif

Utility/Utility/use_atomic.h

@@ -8,13 +8,18 @@
 // on macOS, atomic is available starting with Sierra (Darwin 16)
 // ======================================================================
 
-#if __cplusplus >= 201103L
+#if USING_VISUAL
+    #include <atomic>
+    #define CLHEP_USE_ATOMIC
+#else
+  #if __cplusplus >= 201103L
 
-  #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 7) || __clang__ || USING_VISUAL
+  #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 7) || __clang__ 
     #include <atomic>
     #define CLHEP_USE_ATOMIC
   #endif
 
+  #endif
 #endif
 
 #endif