/*
   * Iterate over all to-be-*newly*-installed solvables
   * those brought in for update reasons are normally *not* reported.
   *
   * if true is passed, iterate over *all* to-be-installed solvables
   *
   * call-seq:
   *  solver.each_to_install { |solvable| ... }
   *  solver.each_to_install(true) { |solvable| ... }
   *
   */
  void each_to_install(int bflag = 0)