Add GRF feature: New Landscape

Custom graphics using actions 1/2/3.

Currently only for rock tiles

src/newgrf_extension.h

@@ -54,6 +54,7 @@ enum Action0RemapPropertyIds {
 	A0RPI_ROADSTOP_MIN_BRIDGE_HEIGHT,
 	A0RPI_ROADSTOP_DISALLOWED_BRIDGE_PILLARS,
 	A0RPI_ROADSTOP_COST_MULTIPLIERS,
+	A0RPI_NEWLANDSCAPE_ENABLE_RECOLOUR,
 };