[fpc-pascal] assigning ansistring with shortstring

[L505]

> > var
> >   filename: string;
> >   last3: string[3];
> >   last4: string[4];
> >   
> this is not short strings
> use
> last3: shortstring[3];

In delphi 5 and FPC  in objfpc mode it doesn't accept that.