Check if visibility is different from current state for a floater

(Should gain some performance as this method is called dozend times per second during UI update)

indra/llui/llfloater.cpp

@@ -600,6 +600,11 @@ LLControlGroup*	LLFloater::getControlGroup()
 
 void LLFloater::setVisible( BOOL visible )
 {
+	// Ansariel: This method is called everytime the UI updates.
+	//           Why should we want to update visibility even
+	//           if nothing has changed?
+	if (visible == LLPanel::getVisible()) return;
+
 	LLPanel::setVisible(visible); // calls handleVisibilityChange()
 	if( visible && mFirstLook )
 	{