Steel Trapdoor.

Adds a steel trapdoor. Textures were painted from scratch, and
inspired by the current Steel Door. Ownership on the trapdoor
works as expected, and so does the crafting recipe.

mods/doors/README.txt

@@ -6,6 +6,7 @@ License of source code:
 -----------------------
 Copyright (C) 2012 PilzAdam
 modified by BlockMen (added sounds, glassdoors[glass, obsidian glass], trapdoor)
+Steel trapdoor added by sofar.
 
 This program is free software. It comes without any warranty, to
 the extent permitted by applicable law. You can redistribute it
@@ -30,11 +31,15 @@ following textures created by celeron55 (CC BY-SA 3.0):
   door_trapdoor_side.png
   door_glass_a.png
   door_glass_b.png
-  
+
 following Textures created by PenguinDad (CC BY-SA 4.0):
   door_glass.png
   door_obsidian_glass.png
 
+Steel trapdoor textures by sofar (CC-BY-SA-3.0)
+  doors_trapdoor_steel.png
+  doors_trapdoor_steel_side.png
+
 All other textures (created by PilzAdam): WTFPL