Remove unnecessary Lua version compatibility

Only Lua 5.1 and LuaJIT need support. The builtin Lua code uses
plain old "unpack" anyway.

.luacheckrc

@@ -1,8 +1,7 @@
 std = "min"
 read_globals = {
 	"default", "digiline", "ItemStack", "mcl_sounds", "mesecon", "minetest",
-	"pipeworks", "table.copy", "table.unpack", "unpack", "VoxelArea",
-	"vector",
+	"pipeworks", "table.copy", "unpack", "VoxelArea", "vector",
 }
 globals = {"minetest.is_protected"}
 ignore = {"21/_.*"}

init.lua

@@ -48,8 +48,6 @@ local function use(dep, keys)
 		for i, key in ipairs(keys) do
 			values[i] = returned[key]
 		end
-		-- The location of unpack() may depend on the Lua version:
-		local unpack = unpack or table.unpack
 		return unpack(values, 1, #keys)
 	else
 		return returned