type as extension for the extension point with name
extension.point.name. gIoExtensionPointImplement(extension.point.name, type, extension.name, priority)extension.point.nametypeGType to register as extensionextension.namepriorityGIOExtension] a GIOExtension object for GTypetype has already been registered as an extension for this
extension point, the existing GIOExtension object is returned.