(svn r20049) -Feature: [NewGRF] Add a railtype flag to disallow level crossings per railtype.

src/ai/api/ai_rail.hpp

@@ -38,6 +38,9 @@ public:
 
 		/** Non-uniform stations is diabled */
 		ERR_NONUNIFORM_STATIONS_DISABLED,  // [STR_ERROR_NONUNIFORM_STATIONS_DISALLOWED]
+
+		/** This railtype cannot have crossings */
+		ERR_RAILTYPE_DISALLOWS_CROSSING,   // [STR_ERROR_CROSSING_DISALLOWED]
 	};
 
 	/**