Merged from trunk -r11833:11841

   Merged from trunk -r11833:11841

   | 11834   | Update docstring for dblink._find_libs_to_preserve().        |
   | zmedico |                                                              |

   | 11835   | Handle a corner case inside                                  |
   | zmedico | dblink._add_preserve_libs_to_contents() in which a path to   |
   |         | be preserved doesn't exist in the contents of the installed  |
   |         | instance.                                                    |

   | 11836   | When adding parent directories to contents inside            |
   | zmedico | dblink._add_preserve_libs_to_contents(), account for the     |
   |         | trailing slash on $ROOT in the while loop.                   |

   | 11837   | Add PROPERTIES=interactive support in depgraph.display() and |
   | zmedico | the PackageCounters class.                                   |

   | 11838   | Move initialization of Scheduler._background from the        |
   | zmedico | constructor to the merge() method so that a potential        |
   |         | InvalidDependString exception can be handled there, causing  |
   |         | merge() to return unsuccessfully. This avoids having to      |
   |         | raise an exception from the constructor.                     |

   | 11839   | Inside Scheduler._reverse_uninstall_edges(), iover all nodes |
   | zmedico | rather than just the merge list, because some uninstall      |
   |         | nodes may not be in the merge list since they will be        |
   |         | performed as part of an upgrade within a slot. This solves a |
   |         | problem with Scheduler._choose_pkg() not parallelizing in    |
   |         | some cases when it should, due to an uninstall node not      |
   |         | having it's edge reversed like it's supposed to.             |

   | 11840   | Make show_invalid_depstring_notice() send output to stderr   |
   | zmedico | via writemsg_level().                                        |

   | 11841   | Remove unused formatter code in                              |
   | zmedico | show_invalid_depstring_notice().                             |

svn path=/main/branches/prefix/; revision=11940