Keep track of the `GParamSpec`s of the properties. This allows us to use
`g_object_notify_by_pspec()`, which is a bit more performant than
`g_object_notify()`(as it doesn't need to take a global lock to lookup
the property name). It also prevents accidental typos in the property
name at compile time.
Also always add `G_PARAM_STATIC_STRINGS`, to prevent some unnecessary
string duplications of property name, blurb and description.
This will allow to have different icons for internal audio cards
(which are flagged generically as "audio-card"), depending on which
port is in use (ie. headphones or speakers).
This requires the new icon information, which is only exported by
PulseAudio 3.0. If it's not available, we fallback to card icons
like before.
https://bugzilla.gnome.org/show_bug.cgi?id=689931
