Upgrade xscreensaver{,-demo} to 5.43
(5.40 started complaining, and we are not Debian ;)

From upstream's changelog:

 5.43	01-Jul-2019

    New hacks, GravityWell, DeepStars.
    GLPlanet now supports the Mercator projection.
    Bouncing Cow has mathematically ideal cows (spherical, frictionless).
    Foggy toasters.
    Unknown Pleasures can now use an image file as a clip mask.
    Updated webcollage for recent changes.
    macOS: Fixed BSOD fonts on UWQHD+ displays.
    X11: Added some sample unlock dialog color schemes to the .ad file.
    X11: On systemd systems, closing your laptop lid might actually
    lock your screen now, maybe.
    X11: 'sonar' can ping without being setuid by using setcap.

5.42	28-Dec-2018

    macOS: Fixed Sparkle auto-updater.

5.41	26-Dec-2018

    X11: Those new font-loading fallback heuristics work again. Oops.
    iOS, Android: Plugged many memory leaks at exit.
    New hack, handsy.
    Fixed noof from displaying minimalistically.
    Rewrote unknownpleasures to be faster, and a true waterfall graph.
    BSOD Solaris improved. DVD added.
    Linux: If the xscreensaver daemon is setuid, then we can implore
    the kernel's out-of-memory killer to pretty please not unlock the
    screen.
    macOS: Upgraded Sparkle (the "Check for Updates" library).
    macOS: Screen saver settings work again on 10.14.


(hauke)