Hide "New Private Tab" item in permanent private browsing mode
(as Firefox hides "New Private Window")
Add "privateTab-isPrivate" atribute to private window
Usage:
#main-window[privateTab-isPrivate] #appmenu-button {
	text-decoration: underline !important;
	-moz-text-decoration-color: white !important;
	-moz-text-decoration-style: dashed !important;
}