Convert digilines to a mod (not modpack). (#32)

Digilines is probably used by most people in its entirety.

I've retained the ability to disable inventory, rtc, lightsensor and
LCD by the minetest settings "diglines_enable_rtc" etc.. If set to
"false", these components will not be loaded. It is assumed by default
that these are enabled.

In the conversion the digilines_lcd:lcd node was renamed to
digilines:lcd (same for all the other nodes). To retain backwards
compatibility I've provided aliases for each of these nodes.

internal.lua

@@ -0,0 +1,90 @@
+function digiline:getspec(node)
+	if not minetest.registered_nodes[node.name] then return false end
+	return minetest.registered_nodes[node.name].digiline
+end
+
+function digiline:importrules(spec, node)
+	if type(spec) == 'function' then
+		return spec(node)
+	elseif spec then
+		return spec
+	else
+		return digiline.rules.default
+	end
+end
+
+function digiline:getAnyInputRules(pos)
+	local node = minetest.get_node(pos)
+	local spec = digiline:getspec(node)
+	if not spec then return end
+
+	if spec.wire then
+		return digiline:importrules(spec.wire.rules, node)
+	end
+	if spec.effector then
+		return digiline:importrules(spec.effector.rules, node)
+	end
+end
+
+function digiline:getAnyOutputRules(pos)
+	local node = minetest.get_node(pos)
+	local spec = digiline:getspec(node)
+	if not spec then return end
+
+	if spec.wire then
+		return digiline:importrules(spec.wire.rules, node)
+	end
+	if spec.receptor then
+		return digiline:importrules(spec.receptor.rules, node)
+	end
+end
+
+function digiline:rules_link(output, input)
+	local outputrules = digiline:getAnyOutputRules(output)
+	local inputrules  = digiline:getAnyInputRules (input)
+
+	if not outputrules or not inputrules then return false end
+
+
+	for _, orule in ipairs(outputrules) do
+		if digiline:cmpPos(digiline:addPosRule(output, orule), input) then
+			for _, irule in ipairs(inputrules) do
+				if digiline:cmpPos(digiline:addPosRule(input, irule), output) then
+					return true
+				end
+			end
+		end
+	end
+	return false
+end
+
+function digiline:rules_link_anydir(output, input)
+	return digiline:rules_link(output, input)
+	or     digiline:rules_link(input, output)
+end
+
+function digiline:transmit(pos, channel, msg, checked)
+	local checkedid = tostring(pos.x).."_"..tostring(pos.y).."_"..tostring(pos.z)
+	if checked[checkedid] then return end
+	checked[checkedid] = true
+
+	local node = minetest.get_node(pos)
+	local spec = digiline:getspec(node)
+	if not spec then return end
+
+
+	-- Effector actions --> Receive
+	if spec.effector then
+		spec.effector.action(pos, node, channel, msg)
+	end
+
+	-- Cable actions --> Transmit
+	if spec.wire then
+		local rules = digiline:importrules(spec.wire.rules, node)
+		for _,rule in ipairs(rules) do
+			if digiline:rules_link(pos, digiline:addPosRule(pos, rule)) then
+				digiline:transmit(digiline:addPosRule(pos, rule), channel, msg, checked)
+			end
+		end
+	end
+end