Add binary format for exporting, with options

Currently I use the .lua map export and trim off everything I don't need/don't use in order to put it into a binary format. I have no need for XML or means to have to parse it. My constraints are in C and C++.

Currently using this script. It would be awesome to be able to not have an additional step to export maps. I would implement it myself, but after delving into the code, I couldn't quite key out where this interaction is.

Similar issues,
#731 - consensus, not implemented due to extendability concerns

if(arg[1] == nil) then
	print("No argument was passed!")
	exit(1)
end

local world = dofile(arg[1])

local out_name = arg[1] .. ".wld"

local fp = io.open(out_name, "wb")

local write = function(self, data)
	self:write(data)
end

local write8 = function(self, data)
	self:write(string.char(data))
end

local write16 = function(self, data)
	local a, b
	a = bit.band(data, 0xFF)
	data = bit.rshift(data, 8)
	b = bit.band(data, 0xFF)
	write8(self, a)
	write8(self, b)
end

local write24 = function(self, data)
	local a, b, c
	a = bit.band(data, 0xFF)
	data = bit.rshift(data, 8)
	b = bit.band(data, 0xFF)
	data = bit.rshift(data, 8)
	c = bit.band(data, 0xFF)
	write8(self, a)
	write8(self, b)
	write8(self, c)
end

local write32 = function(self, data)
	local a, b, c, d
	a = bit.band(data, 0xFF)
	data = bit.rshift(data, 8)
	b = bit.band(data, 0xFF)
	data = bit.rshift(data, 8)
	c = bit.band(data, 0xFF)
	data = bit.rshift(data, 8)
	d = bit.band(data, 0xFF)
	write8(self, a)
	write8(self, b)
	write8(self, c)
	write8(self, d)
end


write(fp, "WLRD\0")
write32(fp, world.width)
write32(fp, world.height)
write8(fp, world.tilewidth)
write8(fp, world.tileheight)
write8(fp, #world.layers)
for layer=1, #world.layers do
	local layer_len = world.layers[layer].width * world.layers[layer].height
	local bpt = 1 -- bytes per tile
	for _, v in next, world.layers[layer].data do
		if(v > 0xFF) then
			bpt = bpt > 2 and bpt or 2
		end
		if(v > 0xFFFF) then
			bpt = bpt > 3 and bpt or 3
		end
		if(v > 0xFFFFFF) then
			bpt = bpt > 4 and bpt or 4
		end
	end
	local write_func = write8
	if(bpt == 2) then
		write_func = write16
	end
	if(bpt == 3) then
		write_func = write24
	end
	if(bpt == 4) then
		write_func = write32
	end
	write8(fp, bpt)
	write32(fp, layer_len * bpt)
	for i=1, layer_len do
		write_func(fp, world.layers[layer].data[i])
	end
end

fp:close()

The data I care about comes out to,
[header][version][width][height][tilewidth][tileheight][num layers]{[bytes per tile][byte length][tiles...]}...

Given issues 731, you stated that there are other things such as properties that are included in the TMX format. I disagree that it not extensible, instead want to offer that on the latest version here it is safe to step away further into this and dump the properties and other data in an easy, loadable way. This means prefixing the length of the data and its offsets. The version can be used to deprecate and add features to the loader. I do think that zlib would be awesome to keep, too. Not sure what tbin is, and appears to be a very specific use case with 4 bytes per tile (ouch).

Another thing, there are a lot of hits on google about this topic. I would love to see tiled grow from an addition like this.

The issue names no source files or tests; start by locating the Lua map export path and the existing TMX export code. Review the proposed binary layout, properties, versioning, and optional zlib support, then define the exporter options and validation needed for a complete implementation.