[3dprinter-general] libsavitar is marked for autoremoval from testing

[Christoph Berg]

Re: Gregor Riepl
> I'm a bit fed up with this. The symbols file should *help* detect
> breaking API changes, not constantly break package builds for no good
> reason.

Plus the C++ mangling is really a pita. c++filt helps a bit, but it's
still horrible. It feels like dpkg-gensymbols could do the unmangling
itself in the diff displayed, that would likely help a lot. But it
doesn't at the moment.

Let's drop them, the libs don't have external users anyway. (Except
maybe for polyclipping, but the symbols don't help there either.)

Christoph