Rename Button.these to Button.check_buttons

Also changed default value of `buttons` argument to be empty list instead
of empty dict.

Author: ddemidov

ev3dev.py

@@ -1767,7 +1767,7 @@ def buttons_pressed(self):
     def any(self):
         return bool(self.buttons_pressed)
 
-    def these(self,buttons={}):
+    def check_buttons(self,buttons=[]):
         if len(buttons) == 0:
             return False
         s = self.buttons_pressed