Instead of the /depends/ directory on chocolate-doom.org which nobody
except me can edit. Also define a variable to define the base URL for
the mirrors repo so that we can update it easily when GitHub change
their URLs.
Since we're downloading arbitrary executable code from websites and
running it, we should at least have some confidence it's the right
thing we're running.
Download these from the maintainers' websites where possible, and
document in a couple of cases why we're still using the mirror. In the
future we can possibly make an automated/generic mechanism for providing
a mirror for files used by chocpkg.
The only place this is needed is when determining the directory name
that the tar file will be extracted to. This can be done by examining
the .tar file name without needing to know the version itself.
These modules encapsulate individual pieces of functionality and make
the code far more maintainable. This is a pretty big refactoring but
overall a big win.
