In order for user to be able to track changes in the value set in
GstTimedValueControlSource the following signals have been added:
* value-added
* value-removed
* value-changed
To be able to use a GstControlPoint to be marshalled into the signals,
the GstControlPoint structure is now registerd as a GBoxed type.
New API:
~~~~~~~
* GstTimedValueControlSource::value-added
* GstTimedValueControlSource::value-removed
* GstTimedValueControlSource::value-added
https://bugzilla.gnome.org/show_bug.cgi?id=737616
Move most of the code to a GstTimedValueControlSource. Split out the trigger
'interpolation mode' to a new control source class. Move tests and examples to
new api. Update docs.
Fixes#610338