All dependencies are now installed only ones. If a port depends on for
examle zlib and one of its other dependencies depends on zlib, zlib will
now get installe only once.
Accept .tgz archives as the main download file
Now ports define some environment variables, and call a unified bash
script that handles configuration, recompilation and installation.
If a port uses non-configure buildsystem, port script can also specify
custom build and install step.
This patch contains simple infrastructure for porting software for
banan-os. I added a doom as the first port. Doom needs a wad file
that you have to aquire yourself. I am not sure if I am allowed to
redistribute doom1.wad (shareware) version so I decided not to.
