[fpc-pascal] old code with readdir

[Marco van de Voort]

> I have old code from freepascal older than 2.0.0, and I want to migrate
> to amd64 debian, but have this error, I have read in googlin about this
> problem but the possible solutions, use oldlinux ( not avaliable with
> this version o freepascal) or baseunix this resolv some of problems but
> not at all.
>  Error: Identifier not found "pdir"
>  Error: Error in type definition
>  Error: Identifier not found "pdirent"
>  Error: Error in type definition
>  (this resolved with baseunix unit) 
>  Error: Identifier not found "opendir"
>  Error: Operator is not overloaded

These have been changed to become more POSIX compliant. To make a clear
break they have been prefixed with fp*

See basenix.fpreaddir etc in the help.

Note that it is nearly always better to use the highlevel Pascal equivalents
findfirst/findnext.