So, I have a 5-button mouse with a scroll wheel.  If I tell X that there's
3 buttons and a scroll wheel, the scroll wheel can be mapped to buttons 4 and
5, and everything works.  If I tell it there's 5 buttons and a scroll wheel,
the wheel gets mapped to buttons 6 and 7.  Thus, for instance, xev shows it as
clicks on buttons 6 and 7... but mozilla still uses buttons 4 and 5 for
scrolling, which is confusing.

It appears that other X apps are correctly seeing buttons 4 and 5 distinct
from 6 and 7.  Is this a mozilla bug, or an X configuration error on my part,
or what?

-s