Update to 2.18 to support libinput 1.31.0

[Alexthemediocre]

Arch Linux is now using libinput 1.31.0. After I updated to this version, all keyboard, mouse, and touchscreen functionality was broken (after unlocking root partition), as described in #19. Running sudo libinput list-devices (from libinput-tools) gives me this output:

libinput-list-devices: /usr/lib/libwacom.so.9: version `LIBWACOM_2.18' not found (required by /usr/lib/libinput.so.10)

[SouthCraftX]

Temporary downgrading to 1.30.1 helps, but I really hope devs can solve the problem.

[Alexthemediocre]

Note: AUR package of libwacom-surface has been updated to 2.18.0-1, which seems to have fixed the issue when using libinput 1.31.0 (simple changes to PKGBUILD, just pulled libwacom 2.18.0 instead of 2.17.0 - commit). Leaving this issue open so (a) this repo can be updated to 2.18.0 and (b) any necessary changes can be made instead of naively applying 2.17.0 patches to 2.18.0 libwacom (which as I understand is what the AUR package did).