Summary:
The pointer constraints protocol is an unstable protocol and thus
the implementation follows the semantics of unstable protocols.
The protocol allows to create a constraint on the pointer - either a
lock or a confinement on a surface. Those are not activated at once, but
when the compositor actively grants it.
During lock no further pointer motion is emitted, during confinement the
pointer is kept in a certain area.
This implements T4451.
Reviewers: #plasma_on_wayland
Subscribers: plasma-devel
Tags: #plasma_on_wayland
Differential Revision: https://phabricator.kde.org/D3466
