[client] Wrap wl_shell_surface_set_{class,title}
Summary: We have to wrap these two requests just for convenience.
Reviewers: KWin, davidedmundson
Reviewed By: KWin, davidedmundson
Subscribers: davidedmundson, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D18440