Fail legacy interfaces if the position is too large for them to represent
HelenOS interfaces support unsigned 64-bit file sizes and offsets. This
is in contrast with C99-ish and POSIX-ish interfaces in libc and libposix.
The legacy API emulation internally uses the native unsigned 64-bit file
sizes and positions and so it may happen that a returned file size or
offset are bigger than the legacy interface can represent. We choose
to report failure in such a case in order to avoid returning wrong