Make wrench usable independently of technic

wrench/depends.txt

@@ -1,6 +1,6 @@
 default
-technic
-technic_chests
-technic_worldgen
+technic?
+technic_chests?
+technic_worldgen?
 intllib?
 

wrench/support.lua

@@ -66,6 +66,8 @@ function wrench:original_name(name)
 end
 
 function wrench:register_node(name, def)
-	self.registered_nodes[name] = def
+	if minetest.registered_nodes[name] then
+	    self.registered_nodes[name] = def
+	end
 end
 

wrench/technic.lua

@@ -323,19 +323,21 @@ for i = 1, 15 do
 	})
 end
 
-for tier, _ in pairs(technic.machines) do
-	local ltier = tier:lower()
-	for i = 0, 8 do
-		wrench:register_node("technic:"..ltier.."_battery_box"..i, {
-			lists = {"src", "dst"},
-			metas = {infotext = STRING,
-				formspec = STRING,
-				[tier.."_EU_demand"] = INT,
-				[tier.."_EU_supply"] = INT,
-				[tier.."_EU_input"] = INT,
-				internal_EU_charge = INT,
-				last_side_shown = INT},
-		})
+if minetest.get_modpath("technic") then
+    for tier, _ in pairs(technic.machines) do
+		local ltier = tier:lower()
+		for i = 0, 8 do
+			wrench:register_node("technic:"..ltier.."_battery_box"..i, {
+				lists = {"src", "dst"},
+				metas = {infotext = STRING,
+					formspec = STRING,
+					[tier.."_EU_demand"] = INT,
+					[tier.."_EU_supply"] = INT,
+					[tier.."_EU_input"] = INT,
+					internal_EU_charge = INT,
+					last_side_shown = INT},
+			})
+		end
 	end
 end