Added dummy Data class for statistics.

Telegram/SourceFiles/data/data_statistics.cpp

@@ -0,0 +1,14 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#include "data/data_statistics.h"
+
+namespace Data {
+namespace {
+} // namespace
+
+} // namespace Data