Moved from last cc65 release (2.13.3) to recent cc65 snapshot (2.13.9).

Relevant cc65 changes...

General:
- The compiler generates "extended" dependency info (like gcc) so there's no need for postprocessing whatsoever :-)
- The linker is very pernickety regarding the ordering of cmdline options so a custom linker rule is necessary :-(

Apple2:
- The various memory usage scenarios aren't specified anymore via separate linker configs but via defines overriding default values in the builtin linker config.

Atari:
- The builtin linker config allows to override the start addr so there no more need for a custom linker config.
- The C library comes with POSIX directory access. So there's no more need for for a custom coding.

CBM:
- The C library comes with POSIX directory access. So there's no more need for for a custom coding.