Allow turning flying on and off while seated, if using Continue Fly On Unsit

Note: Redundant code, but these functions will likely be merged eventually(FUI-esque project), so it doesn't matter for now.

indra/newview/lltoolbar.cpp

@@ -307,7 +307,12 @@ void LLToolBar::refresh()
 	setVisible(show && !mouselook);
 
 	BOOL sitting = FALSE;
-	if (gAgentAvatarp)
+	static LLCachedControl<bool> continue_flying_on_unsit("LiruContinueFlyingOnUnsit");
+	if (continue_flying_on_unsit)
+	{
+		sitting = false;
+	}
+	else if (gAgentAvatarp)
 	{
 		sitting = gAgentAvatarp->isSitting();
 	}