BF: memory leak in RatingScale (reduce its severity)

- likely due to leak in TextStim, where setText does not release mem for old text
- partial solution = avoid doing setText every frame, use only when needed

psychopy/visual/ratingscale.py

@@ -1021,9 +1021,11 @@ def draw(self, log=True):
                     else:
                         valTmp = self.markerPlacedAt + self.low
                         val = self.fmtStr % (valTmp * self.autoRescaleFactor)
-                    self.accept.setText(val)
+                    if self.accept.text != val:  # not just for speed: reduce impact of mem leaks in TextStim
+                        self.accept.setText(val)
                 elif self.markerPlacedAt is not False:
-                    self.accept.setText(self.acceptText)
+                    if self.accept.text != self.acceptText:
+                        self.accept.setText(self.acceptText)
 
         # handle key responses:
         if not self.mouseOnly: