Issue title: Addition of a build system generator
 Issue body: I suggest to reuse a higher level build system than your current [small make file](https://github.com/ericfischer/datamaps/blob/09c6b67912d4840827bd8b01e6384d6942758f2e/Makefile#L1) so that powerful checks for software features will become easier.
- [CMake](http://cmake.org/)
- [Autotools](http://www.gnu.org/software/autoconf/#TOCintroduction)

 Comments: 
 Comment 0: The Makefile is already more complicated than I want it to be, actually. I'd like to get rid of the pkg-config stuff and just say -lpng if I could get away with it.

 Comment 1: Are you interested in portable make files?
How do you think about to improve software portability by feature checks?

 Comment 2: No, I would in general like to depend only on facilities that exist on any reasonably modern Unix system.

 Comment 3: There are some variations to consider for implementation details to be safe ...

 Comment 4: As far as I know, everything I am doing is platform-neutral for the platforms I am targeting.

 Comment 5: Does [a tool like "autoscan"](https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/autoscan-Invocation.html) show any software dependencies that you find worth for further considerations?

 Comment 6: +1
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