pppd: Explicitly ship pppd shared object files

pppd: Explicitly ship pppd shared object files

These are needed by pppd, but were not previously shipped as such.
Instead, since their parent directory at /usr/lib/pppd/${version}/ was
not commented out, we implicitly shipped the entire directory.

This patch does not change our behaviour in the end, but makes things
more transparent to developers.

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>