Make Page up/down active in playback mode

The page-up and page-down keys are used to go forwards and backwards one page in the score. However, these keys are inactive when the score is being played. It would be useful if the page up/down keys were active during playback. When the page-down key is pressed, for example, the music would advance to the next page, and the playback would start at the first measure on the new page. Likewise, when the page-up key is pressed, the display would progress to the previous page and start playing at the first measure of the new page.