Not referencing them caused them to be missing from the source packages.
This also moves all files that were in different dirs under the common
additional-files dir.
* Dosbox is not only a standalone application, it is also used to run
DOS executables non-interactively
* There are several front-ends for it which could be put in $appsDir
* In either case, things are simpler if Dosbox is in the path, it would
not be if installed in home/config/apps.
* Referring the current haiku version explicitly is not needed, since
the RequiresUpdater takes care of setting the version of Haiku used
for building a package.
