Add Win8+ Pointer Input Message for tablet support

This uses Pointer Input Messages for Windows Ink support, with
right-click button, 1024 levels of pressure, rotation and tilt support.

An option is added to enable this support. It cannot be used together
with WinTab at the moment.

Let's say it is EXPERIMENTAL.

CCBUG: 382946
Maniphest Tasks: T6807
Differential Revision: https://phabricator.kde.org/D7441