Minor cleanup around security cameras / viewscreens. DONT_BUILD.
The only semantic change is that an out-of-sync instance of a distance to
check (viewscreen sprite <-> player sprite) is changed in
actors.c:G_MoveStandables(), from 2048 (as in Duke3D 1.5) to 8192, now
represented by the define VIEWSCREEN_ACTIVE_DISTANCE. I have not yet observed
any change in behavior regarding this change (but there ought to be one).
Also, in DNCOORDS display, print 'totalclock' count, too.