I wasn't completely sure what to do with the registry key. Keeping "Wine/X11 Driver" is a bit odd, but it also makes sure we stay backward compatible. Changing it would require more changes elsewhere and maybe it could be done later, if / when more options are moved.
-- v2: win32u: Move fullscreen window cursor clipping from winex11. winex11: Move clip_fullscreen_window foreground check inside it. win32u: Add a clipping_cursor member to user_thread_info. win32u: Add a clipping_reset member to user_thread_info. win32u: Move grab_pointer registry option from winex11. winex11: Remove now unnecessary WM_X11DRV_CLIP_CURSOR_NOTIFY.