shared thread position for physical/virtual Pure;

prefer Synchronized.var;

tuned signature;

virtual Pure is single-threaded to avoid confusion with multiple thread farms etc.;

tuned signature;

tuned signature -- closer to Exn.Interrupt.expose in Scala;

clarified bootstrap;

clarified context; avoid Unsynchronized.ref;

old;

ensure globally unique counter results;

tuned;

clarified modules;

backout 930a30c1a9af: leads to odd effect of command-line options becoming persistent preferences;

eliminated ancient TTY-based Tactical.tracify and related global references;