Add setting to disable NewGRF inflation flag

src/newgrf.cpp

@@ -9995,7 +9995,7 @@ static void InitializeGRFSpecial()
 	                   |                                                       (1U << 0x1F); // any switch is on
 
 	_ttdpatch_flags[4] =                                                       (1U << 0x00)  // larger persistent storage
-	                   |             ((_settings_game.economy.inflation ? 1U : 0U) << 0x01); // inflation is on
+	                   | ((_settings_game.economy.inflation && !_settings_game.economy.disable_inflation_newgrf_flag ? 1U : 0U) << 0x01); // inflation is on
 	MemSetT(_observed_ttdpatch_flags, 0, lengthof(_observed_ttdpatch_flags));
 }
 

src/settings_type.h

@@ -701,6 +701,7 @@ struct EconomySettings {
 	bool   infrastructure_maintenance;       ///< enable monthly maintenance fee for owner infrastructure
 	uint8  day_length_factor;                ///< factor which the length of day is multiplied
 	uint16 random_road_reconstruction;       ///< chance out of 1000 per tile loop for towns to start random road re-construction
+	bool disable_inflation_newgrf_flag;      ///< Disable NewGRF inflation flag
 };
 
 struct LinkGraphSettings {

src/table/settings/settings.ini

@@ -3193,6 +3193,12 @@ strval   = STR_JUST_COMMA
 cat      = SC_BASIC
 patxname = ""economy.random_road_reconstruction""
 
+[SDT_BOOL]
+var      = economy.disable_inflation_newgrf_flag
+def      = false
+cat      = SC_EXPERT
+patxname = ""economy.disable_inflation_newgrf_flag""
+
 ##
 [SDT_VAR]
 var      = pf.wait_for_pbs_path