Most of this change is a conversion of the old FileDetails struct
into a new LocalFileDetails class. The new class keeps the
members private, and keeps the Unicode and MOR representations of
the string separate.
The NuFX and DiskImg libraries don't support UTF-16 filenames,
so we stil can't add files with non-CP-1252 filenames, but we're
a step closer.
Also, update NufxLib with a couple of fixes from the main project.
Also, fix handling of "%00" when adding files.
Also, mark most of the A2FileDOS fields private. Not sure why
they weren't.
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