x11/xsnow: update to 3.5.3 release (+)

version 3.5.3
01: main.c: drawit(): do now draw the first second or so to hide
    unstable configurations of scenery, stars, etc.
    fallensnow.c, birds.c, aurora.c: make them C++ compliant by
      rewriting goto and typecast pointer assignment
    meteor.c: rewrite goto
    santa.c: continue Santa animation, irrespective of His speed
    fallensnow.c: paint fallensnow one pixel higher
    fallensnow.c: generate more snow when Santa is ploughing
02: loadmeasure.c: maximum 5 warnings about to busy system
03: doit.h: change defaults for aurora_width/height to 60/30

Full changelog:	https://www.ratrabbit.nl/ratrabbit/xsnow/changelog/index.html