[Coco] Drive letter issue in paths with toolshed os9 copy command on Windows

[Guillaume Major]

> One could check if the colon is followed by a number (one or more
> digits). However, C:123FILE is maybe valid also? One would need to
> check that everything following the colon (until comma or end) is
> composed out of digits or a plus (the +offset syntax for HDBDOS
> offset). Can a filename be just a number (without extension) on MSDOS?
> Maybe we can live with that corner case being broken.
>

Yes, a filename can be just a number on Windows. But I think this is the 
best solution because it will handle all other cases. I can live with that!

Guillaume