Use toggleTabPrivate() for TabRemotenessChange -> fixTabRemoteness()

(to check for last private tab and to dispatch PrivateTab:PrivateChanged API event)
(related to #244)

bootstrap.js

@@ -2252,18 +2252,7 @@ var privateTab = {
 			return;
 		}
 		_log(e.type + ": force make tab " + _p(isPrivate));
-		if(this.isRemoteTab(tab)) {
-			var mm = tab.linkedBrowser.messageManager;
-			this.sendAsyncMessage(window, mm, {
-				action: "ToggleState",
-				isPrivate: isPrivate,
-				silent: true
-			});
-		}
-		else {
-			var privacyContext = this.getTabPrivacyContext(tab);
-			privacyContext.usePrivateBrowsing = isPrivate;
-		}
+		this.toggleTabPrivate(tab, isPrivate);
 	},
 	setWindowBusy: function(e, busy) {
 		_log("setWindowBusy(): " + busy);