file_cpy (STRING* destname, STRING* srcname)
Copies or unpacks the file "srcname" to the file"destname". The source file "srcname" will be searched first in the save_dir folder, then in the game folder. If it isn't in both, but ends with ".pak", it will be also searched in the .wrs resource-files. This way a file within a resource can be unpacked and renamed with it's original file ending. If there already is a file with the name"destname" in the save_dir folder, it will be written over.