msdos already transfroms for Windows long names a '/' char into '?'.

msdos already transfroms for Windows long names a '/' char into '?'.
Do the same for the 8.3 case as well.

This is not ideal since now it is possible that two files in the same
directory have the same name but the msdos code already does a lot of
this and so the problem already exists.

OK beck@ miod@