XQuartz: translate additional mouse buttons

Old behavior was to translate the middle mouse button, as well as
every other button that isn't the left or right mouse button,
to act as the middle mouse button (2).

New behavior is to translate only the middle mouse button to 2,
and translate higher-numbered buttons to 8 and higher.
This allows additional mouse buttons to behave under XQuartz
more like they do by default under X11 on other platforms
(e.g. Linux and BSD distributions).

Signed-off-by: Christopher Chavez <chrischavez@gmx.us>
3 jobs for xquartz-buttons in 5 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Docker Image
passed #451492
debian-testing

00:00:31

 
  Build And Test
passed #451493
autotools-build-and-test

00:05:26

passed #451494
meson-build-and-test

00:01:57