Add support for zlib compression with miniz (#163)

[FiniteReality]

This allows users of luvi to use zlib compression without the zlib module, meaning that it is technically no longer necessary.

This has been tested on Debian buster (current testing) on a 64-bit AMD processor, where it appears to work correctly. I expect it to work correctly on all current targets.

I believe I have followed the style of code in my edits, though I will gladly fix any issues that are pointed out.

The API looks something like this, using the example of a deflator:

local miniz = require("miniz")
local deflator = miniz.new_deflator() -- optionally accepts the compression level to use
local deflated, err, partial = deflator:deflate("input text") -- optionally accepts a flush mode to use
-- if there was an error, deflate returns nil, the error that occured, as well as any partial data it managed to compress before an error occured.
print("Deflated data:")
print(deflated or partial)
if err then
    print("Error:")
    print(err)
end

[SinisterRectus]

Make sure everything uses 2 space indentations.

[FiniteReality]

Whoops, there goes KDevelop reindenting my code 😛

[SinisterRectus]

Why is this not an enum?

[FiniteReality]

Lua requires a string array for luaL_checkopt, which is where this is used.

[SinisterRectus]

You probably want to use optint to stay consistent with inflate and deflate.

[FiniteReality]

Those functions appear to use an integer because it's a bitfield, rather than an enumeration. Personally, I think using a string is more favourable here but I will gladly change it.

[SinisterRectus]

I guess either works.

[creationix]

How much does this increase the binary size?

[FiniteReality]

With the patch, binary size is increased by exactly 8 KiB on my machine.

[SinisterRectus]

I know that zlib can optionally be used in luvi, but I was hoping that we could make the most out of miniz since it's included by default. I didn't realize that parts of it were disabled to keep the file size small.

[creationix]

8kb is probably fine. Especially if it enables more apps to use the tiny version of luvi.