Linphone ready for experimental

[Bernhard Schmidt]

Hi Toddy,

since the last dependency of an up-to-date linphone is now in
experimental I have tested to build your current linphone repo. I needed
to make some small changes

https://salsa.debian.org/pkg-voip-team/linphone/commits/fix-build-for-exp

but with these fixes merged, I could successfully build and run linphone
(gtk) in experimental.

Best Regards,
Bernhard