Added castle<->snow forest transition

data/terrain-graphics.cfg

@@ -31,9 +31,11 @@
 # Castle-specific transitions. Those are placed before base terrains, as they
 # override the normal base terrain.
 {CASTLE_TRANSITION CK f forest-ctrans}
+{CASTLE_TRANSITION CK F snow-forest-ctrans}
 {CASTLE_TRANSITION CK T tropical-forest-ctrans}
 #Special cases for encampment (nw, nw-n-ne and ne)
 {CASTLE_TRANSITION nK f forest-etrans}
+{CASTLE_TRANSITION nK F snow-forest-ctrans}
 {CASTLE_TRANSITION nK T tropical-forest-ctrans}
 #On the rest fall back on forest-castle
 {CASTLE_TRANSITION nK f forest-ctrans}