I imagine this must have been noticed by others, and is likely on
someone's ToDo list anyway, but it can't hurt to point it out if I
keep it brief...
With the tabs displayed, when I push the page-down key, it doesn't
put the line that was at the bottom on the top line like it used to.
That line is off the top of the window now.
I looked at `window-height', and see that it accounts for the
modeline and possible scrollbar, but it does not (yet) account for
the tab gutter, and needs to. I am not capable at this time of
making that patch, or I would. I just plain don't understand things
well enough yet to monkey with it.