Use auto for unique pointers

samples/exifdata.cpp

@@ -184,8 +184,7 @@ int main(int argc,const char* argv[])
 	}
 
 	if ( !result ) try {
-		Exiv2::Image::UniquePtr image = Exiv2::ImageFactory::open(file);
-		assert(image.get() != 0);
+        auto image = Exiv2::ImageFactory::open(file);
 		image->readMetadata();
 		Exiv2::ExifData &exifData = image->exifData();