Update platform classes to use OVERRIDE / FINAL when needed

Source/platform/PODArena.h

Index: Source/platform/PODArena.h
diff --git a/Source/platform/PODArena.h b/Source/platform/PODArena.h
index ad6852e5c617790456ef46bdf047a2ddbeeaad64..db3a1d565c48a94d24d316ea5829c5312cb206ab 100644
--- a/Source/platform/PODArena.h
+++ b/Source/platform/PODArena.h
@@ -64,8 +64,8 @@ public:
             return adoptRef(new FastMallocAllocator);
         }
 
-        virtual void* allocate(size_t size) { return fastMalloc(size); }
-        virtual void free(void* ptr) { fastFree(ptr); }
+        virtual void* allocate(size_t size) OVERRIDE { return fastMalloc(size); }
+        virtual void free(void* ptr) OVERRIDE { fastFree(ptr); }
 
     protected:
         FastMallocAllocator() { }