x11/xscreensaver: Update 6.10 => 6.12

6.11 introduced Wayland support, however we leave respective option off
by default as locking is not supported yet, and support generally may be
not mature yet.

Changelog 6.11:

• X11: Now supports Wayland (blanking only, not locking).
• X11: More reliable and timely DPMS activation.
• X11: Dead keys work in password input.
• X11: Fixed a couple of minor Y2038 bugs.

Changelog 6.12:

• X11: DPMS works on Wayland.
• X11: Fading uses GL now which should be more performant.

https://www.jwz.org/xscreensaver/changelog.html

PR: 288834