Add AI/GS methods to get inflation factors

See: #415

src/script/api/script_inflation.cpp

@@ -0,0 +1,24 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file script_inflation.cpp Implementation of ScriptInflation. */
+
+#include "../../stdafx.h"
+#include "script_inflation.hpp"
+#include "../../economy_func.h"
+
+#include "../../safeguards.h"
+
+/* static */ int64 ScriptInflation::GetPriceFactor()
+{
+	return _economy.inflation_prices;
+}
+
+/* static */ int64 ScriptInflation::GetPaymentFactor()
+{
+	return _economy.inflation_payment;
+}