message: change expr::some() to use constant 3 instead of 0
  constant 0 often destroys syntactic equality and confuses quantifier instantiation
diff: @@ -258,7 +258,7 @@ expr expr::mkFreshVar(const char *prefix, const expr &type) {
  }
  expr expr::some(const expr &type) {
  - return type.isBool() ? expr(false) : mkNumber("0", type);
  + return type.isBool() ? expr(false) : mkNumber("3", type);
  }
  expr expr::IntSMin(unsigned bits) {
  