[next] Remove dbus-glib GTypes from public API: TpSvc* signals

Submitted by Simon McVittie

Assigned to Telepathy bugs list

+++ This bug was initially created as a clone of Bug #76369 +++

We should make sure that dbus-glib isn't exposed in our high-level API. One thing we can do is to stop TpSvc* interfaces from emitting signals.

Here are the signals that were mandated by dbus-glib and are also used as GObject signals:

---- potentially emitted by base classes ----

Connection (all CMs): "status-changed",

Used just about everywhere; needs special-casing

Channel (all CMs): "closed",

Used extensively, special case needed

"content-added",
"content-removed",
"call-state-changed",

Used in Gabble, special case probably needed

TLSCertificate (potentially all CMs): "accepted", "rejected",

Used in Gabble and Haze. We could emit normal signals adjacent to these.

---- only emitted by CM/MC code ----

Account (MC): "removed" ChannelDispatcher/CDO/CR (MC): "finished", "failed", "succeeded",

Those are actively used in MC. We could turn them into normal signals and emit them adjacent to tp_svc_foo_emit_bar().

Version: git master