test: change device for enabling/disabling bits to use REL_*

No real effect on the test, this check is just so that a follow-up patch to
fix the tests for the new uinput backend is a bit easier to review.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Make the tests optional to drop unneeded dependencies

libevdev has no external dependencies and both check and libudev are
only required for running the unit-tests. Make them optional.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
test: devices with abs axes need to be created properly

Simply enabling the bits is not enough, we need to provide axis
information too if we want to enable this properly.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Minor documentation improvement

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Simplify a bit state setter

set_bit_state does exactly what the previous if/else did.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>