Add perpendicular and 45/90 degree crossing rails

Add a set of new models for crossings to make some new track
arrangements possible. This commit adds perpendicular crossigns that can
be rotated at any angle: 30/45/60/90 and 45/90 degree crossings in two
rotations. In future, further crossing types can be added to the blender
file.

Add the blender file in rail_crossings.blend that is the source of these
files and which refers to the texture inside advtrains_train_track.

Add a set of prototypes for rail crossings to advtrains/tracks.lua and
register the new crossings in advtrains_train_track.

advtrains/tracks.lua

@@ -210,6 +210,37 @@ advtrains.ap.t_45deg={
 	},
 	rotation={"", "_30", "_45", "_60"},
 }
+advtrains.ap.t_perpcrossing={
+	regstep = 1,
+	variant={
+		st={
+			conns = { {c=0}, {c=8}, {c=4}, {c=12} },
+			desc = "perpendicular crossing",
+			tpdouble = true,
+			tpsingle = true,
+			trackworker = "st",
+		},
+	},
+	regtp=true,
+	tpdefault="st",
+	rotation={"", "_30", "_45", "_60"},
+}
+advtrains.ap.t_9045crossing={
+	regstep = 1,
+	variant={
+		st={
+			conns = { {c=0}, {c=8}, {c=2}, {c=10} },
+			desc = "45/90 degree crossing",
+			tpdouble = true,
+			tpsingle = true,
+			trackworker = "st",
+		},
+	},
+	regtp=true,
+	tpdefault="st",
+	rotation={""},
+}
+
 advtrains.trackpresets = advtrains.ap
 
 --definition format: ([] optional)

advtrains_train_track/init.lua

@@ -11,6 +11,29 @@ advtrains.register_tracks("default", {
 	description=attrans("Track"),
 	formats={},
 }, advtrains.ap.t_30deg_flat)
+
+-- Diamond Crossings
+-- perpendicular
+advtrains.register_tracks("default", {
+	nodename_prefix="advtrains:dtrack_xing",
+	texture_prefix="advtrains_dtrack_xing",
+	models_prefix="advtrains_dtrack_xing",
+	models_suffix=".obj",
+	shared_texture="advtrains_dtrack_shared.png",
+	description=attrans("Perpendicular Diamond Crossing Track"),
+	formats = {}
+}, advtrains.ap.t_perpcrossing)
+-- 45-90(
+advtrains.register_tracks("default", {
+	nodename_prefix="advtrains:dtrack_xing4590",
+	texture_prefix="advtrains_dtrack_xing4590",
+	models_prefix="advtrains_dtrack_xing4590",
+	models_suffix=".obj",
+	shared_texture="advtrains_dtrack_shared.png",
+	description=attrans("45/90 Degree Diamond Crossing Track"),
+	formats = {}
+}, advtrains.ap.t_9045crossing)
+
 --slopes
 advtrains.register_tracks("default", {
 	nodename_prefix="advtrains:dtrack",