(svn r9371) -Feature: Add support for variable snow lines in the arctic climate, supplied

by newgrf files. When this is enabled forests cannot be built below the highest
snow line, and farms can't be built above it. Houses still use the
_opt.snow_line so they are all consistent, so to make them respect the snowline
you may want to use some newhouses features as well.

src/newgrf.cpp

@@ -27,6 +27,7 @@
 #include "fontcache.h"
 #include "date.h"
 #include "currency.h"
+#include "landscape.h"
 #include "sound.h"
 #include "newgrf_config.h"
 #include "newgrf_house.h"
@@ -1510,6 +1511,22 @@ static bool GlobalVarChangeInfo(uint gvid, int numinfo, int prop, byte **bufp, i
 			break;
 
 		case 0x10: // 12 * 32 * B Snow line height table
+			if (numinfo > 1 || IsSnowLineSet()) {
+				grfmsg(1, "GlobalVarChangeInfo: The snowline can only be set once (%d)", numinfo);
+			} else if (len < SNOW_LINE_MONTHS * SNOW_LINE_DAYS) {
+				grfmsg(1, "GlobalVarChangeInfo: Not enough entries set in the snowline table (%d)", len);
+			} else {
+				byte table[SNOW_LINE_MONTHS][SNOW_LINE_DAYS];
+
+				for (uint i = 0; i < SNOW_LINE_MONTHS; i++) {
+					for (uint j = 0; j < SNOW_LINE_DAYS; j++) {
+						table[i][j] = grf_load_byte(&buf);
+					}
+				}
+				SetSnowLine(table);
+			}
+			break;
+
 		default:
 			ret = true;
 	}
@@ -3973,6 +3990,9 @@ static void ResetNewGRFData()
 	ResetStationClasses();
 	ResetCustomStations();
 
+	/* Reset the snowline table. */
+	ClearSnowLine();
+
 	/* Reset NewGRF files */
 	ResetNewGRF();