[sigc] Don't package libsigc++ 2.0.2

[Murray Cumming <murrayc murrayc com>]

Bradley, I think it would be best not to package libsigc++ 2.0.2, or to
stop it from moving into stable if it has already been packaged. It
seems to cause lots of application crashes.

Because libsigc++ is mostly headers, you'll need to rebuild most
applications that were built with libsigc++ 2.0.2, to fix the crashes.

-- 
Murray Cumming
murrayc murrayc com
www.murrayc.com