Drop the subtypes, and keep a single udev-based GsdDeviceManager,
which will work on both backends, and should work on all platforms
we care about (?).
Those files are no longer existent in gnome-settings-daemon, so
this module is free to do as it pleases with them, there doesn't
need to exist any synchronization anymore.
Meson is a build system focused on speed an ease of use, which
helps speeding up the software development. This patch adds meson
support along autotools.
https://bugzilla.gnome.org/show_bug.cgi?id=785414
