`fnmerge` and `fnsplit` haven't been implemented since I noticed inconsistencies in the documentation relating to them, for now I simply have empty function definitions in the form described by  https://www.digitalmars.com/rtl/direct.html (ie no `_` prefix)
The status of other functions is as follows:
`_chdir`, `_chdrive`: impossible to implement, succeeds without an error code, or change of state in the Xbox
`_getcwd`, `_getwd`: impossible to implement, return NULL pointers and sets `errno` to `-EINVAL`
`_getdrive`: as before, impossible to implement - returns `0` and sets `errno` to `-EINVAL` (this is the error state described by a combo of MS public documentation and digital mars docs)
`_searchpath`: impossible to implement since there is no PATH variable on the Xbox
`_mkdir`, `_rmdir`: implemented, testing required, however

…errors