Use an enum to enable/disable tapping configuration

More expressive in the caller and less ambiguous about return values (is it 1?
is it non-zero? can it be negative?)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
tools: always enable tapping in the event-gui program

This is a debugging tool, so the features to debug should be enabled by
default.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>