ECS fixes

-fixed bug with addEntityCopy (on create was called for bad entity, and incorrect block was added to update)
-added function to retrieve Component pointer from Entity (not  template function)
-fixed thread_pool bug

demos/external/sources/mmutils/thread_pool.d

@@ -396,8 +396,8 @@ version (MM_USE_POSIX_THREADS)
 		void start(DG dg)
 		{
 			threadStart = dg;
-			int ok = pthread_create(&handle, null, &threadRunFunc, cast(void*)&this);
-			if(!ok)handle = pthread_t();
+			int err = pthread_create(&handle, null, &threadRunFunc, cast(void*)&this);
+			if(err)handle = pthread_t();
 			//assert(ok == 0);
 		}