The Linux port's get_resource function seems to be using the original
filenames, rather than the 8.3 filenames used by the Windows EXE's
resource system. Too bad it doesn't tell us the original file extensions.
This way, we don't need to tell everyone who uses the enhanced branch
that they need to copy res/data_en. It also gives the CMake project a
way to bundle everything into a neat little folder.
