Joaquim Rocha authored Jan 18, 2018 and Richard Hughes committed Jan 25, 2018

Sometimes we cannot apply an action to a GsApp right away (e.g. because
of not having an available worker thread for the action), so we should
be able to set up an internal state in GsApp objects in order to reflect
this.

For that purpose, this patch introduces a gs_app_get/set_pending_action
private method that can be used to track and eventually inform the user
about this condition.