The stream status message object may be of a non-GObject type, e.g.
G_TYPE_POINTER (see GstAudioSrc), so print that properly instead
of assuming the value holds an object.
Remove the static function set on the TaskPool before _prepare() is called and
allow for assigning a function to a Task when we _push().
Update the examples
Add an example to demonstrate the use of a custom taskpool and how to configure
it on the task. Currently the taskpool does not do much yet but it'll create
some custom threads later on.