Building GD-2.0.33 library on OpenBSD 3.8

Unaltered, it gives a compilation error (well at least it did in my case), complaining of png.h being unavailable. That is because configure script does not properly set -I compilation option. It sets it to /usr/local/include/libpng/libpng, whereas just /usr/local/include/libpng would be enough. For brute force solution just edit Makefile, find and delete a redundant libpng string from -I option.I sent an e-mail to GD maintainers so that they might consider a proper fix at some point.