With the dependencies captured in manifest.py, several packages in
python-stdlib were still unix-only due to direct or transitive dependencies
on unix-only or ffi modules. Or they just make no sense to run on
microcontroller targets.
In a few cases (e.g. base64) where possible, the unix dependency could be
removed.
Updates manifest.py to use the `unix_ffi=True` arg to `require()` for these
libraries.
Rename re-pcre to re now that unix-ffi is effectively its own namespace.
Update unix-ffi/README.md, and strengthen the wording that the unix
libraries are unmaintained.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
Jim Mussared