Message 251692 - Python tracker

By reading http://www.tcl.tk/man/tcl8.6/TkCmd/text.htm I discovered that Text.yview(index) puts the line with index at the top of the windows, given enough line below to fill the window.  This fixes another glitch.

Still left: the original 3 items (msg251181), navigating the text with up and down arrow (msg251571), and operating TOC button with keyboard (msg251556).