Add support for systems without udev (e.g. Gentoo)

Some systems like Gentoo do not run udev by default. Gentoo has a fork named eudev:

https://wiki.gentoo.org/wiki/Eudev

This prevents interception from working properly.

See this caps2esc issue: interception/linux/plugins/caps2esc#2 (closed)

It would be great to extend support beyond udev.