Max value of the volume popups shouldn't go up to 400

[Gimmeapill]

in https://github.com/Buzztrax/buzztrax/blob/master/src/ui/edit/volume-popup.c

// FIXME(ensonic): workaround for https://bugzilla.gnome.org/show_bug.cgi?id=667598 g_sprintf (str, "%3d %%", 400 - (gint) (gtk_range_get_value (range))); gtk_label_set_text (label, str); }

According to the comments this was a workaround for https://bugzilla.gnome.org/show_bug.cgi?id=667598 which is marked as closed, so it could maybe be reverted to a more usable value like 100?

Default value should also be a bit lower than 100 to avoid running straight away into clipping issues.
A more sensible value should probably be around 75-80% like old Buzz.

[ensonic]

The workaround is using 0.0 ... 400.0 as a range istead of 0.0 ... 100.0. The choice of an upper bound > 100% is intentional to also allow making quite machines louder.

The default value of 100% is choose so that by default nothing is changed. Let me check on the default in buzz. But if we want to change this we need to come up with a backwards compat way of changing it.