Algorithm
=========
The bin pack 2D algorithm used was taked off this web page
http://codeincomplete.com/posts/2011/5/7/bin_packing/. I've looked at this one,
and two other alternatives, but this was extremely straightforward to
understand and implement, so I went with it.

Building
========
Given you have SDL2, SDL2_image and libPNG, it should be as simple as:

  make build

And you should have a imgpacker binary on the same folder.

The program is built with debugging and assertions turned on. You'd have to
change Makefile to have something like an optimized build.

Notes on GNU Make
=================
The make file is pretty simple, but I've only used GNU make. Besides, I can't
guarantee it'll work on different versions of the make utility.

The Use of AllocUtil
====================
I've written a library called AllocUtil containing some utilities for dealing
with dynamically allocated memory (https://github.com/phao/AllocUtil). This
program (imgpacker) is the first program I write which uses AllocUtil.
Strangely enough, it all worked just right from the first time, which is kind
of both scary and gratifying.

Names
=====
Currently, this code uses lower case identifiers with underscores for
separations. This doesn't match the naming style I'm going for these days, so
I'll probably be changing it in the future.