High-resolution scroll wheel support

Description:

See Mutter MR for description and build instructions.

Windows

The 120 based value API is a copy of the Windows API. I don't have access to a Windows machine, but high-resolution scroll support on Windows should be pretty easy to achieve after merging this MR.

Status

• libinput: Merged
• Wayland: Merged
• Mutter: mutter!1962 (merged)
• GTK: This PR
• xf86-input-libinput: X11, merged

For code reviewers

It's easier to review this PR commit by commit.

Supersedes !1624 (closed)

cc @whot @carlosg