(svn r12924) -Feature: Introducing the so called 'engine pool' which primarily removes the fixed engine type limits and also happens to allow (with the patch option 'dynamic_engines') multiple NewGRF vehicle sets to coexist.

src/settings_type.h

@@ -232,6 +232,8 @@ struct Patches {
 	bool give_money;             ///< allow giving other players money
 
 	bool enable_signal_gui;      ///< Show the signal GUI when the signal button is pressed
+
+	bool dynamic_engines;    ///< Enable dynamic allocation of engine data
 };
 
 extern Patches _patches;