a string of the form "signal-name::detail".
The interface/instance type that introduced "signal-name".
Location to store the signal id.
Location to store the detail quark.
%TRUE forces creation of a #GQuark for the detail.
Whether the signal name could successfully be parsed and @signal_id_p and @detail_p contain valid return values.
Internal function to parse a signal name into its @signal_id and @detail quark.