Windlight floaters' isOpen() functions were always returning true after singleton was created, regardless of current visiblity status. Resulted in pointless syncMenu calls which are very expensive.

indra/newview/llfloaterwindlight.cpp

@@ -473,7 +473,7 @@ void LLFloaterWindLight::show()
 bool LLFloaterWindLight::isOpen()
 {
 	if (sWindLight != NULL) {
-		return true;
+		return sWindLight->getVisible();
 	}
 	return false;
 }