Removed "label" properties which no longer have any function.
Labels are still used as layer names and as identifiers for sending
behaviors between sides of a split keyboard, so those have been left
alone for now.
* Allows removing multilib from docker images
* Run properly in aarch64 host docker
containers for testing on Rasberry Pi.
* Small sticky-keys fix to initialize w/ correct
constant for max uin32_t value.
The current combo completion check only makes sure the last key in the
combo is set. This works when the combo is typed correctly initially, or
when reraising events in a combo of length two. However, it fails for
longer combos since the last event in pressed_keys might be set, but the
first (or subsequent) event in pressed_keys can be NULL thanks to
release_pressed_keys.
Also added a regression test.
