GUPnP 0.19 Unstable cycle

[Jens Georg <mail jensge org>]

Hi.

After we kind of skipped the last unstable cycle, I really would like to
use this cycle properly.

If noone objects I will move master into a state where it's possible to
break API and ABI so we can merge all the patches that have accumulated
which would do so, including the connman patch with its glib 2.28
dependency.

By moving state I mean: gupnp-0.20.pc and GUPnP-0.20.gir file and bump
the soname.