Merged from trunk -r12117:12126

   Merged from trunk -r12117:12126

   | 12120   | Add 'automatically resolved' blockers to the --pretend docs. |
   | zmedico |                                                              |

   | 12122   | Add a sanity check inside depgraph._add_pkg() to ensure that |
   | zmedico | the dependencies of the same package are never processed     |
   |         | more than once.                                              |

   | 12124   | Change depgraph._slot_collision_info() from a set to a dict  |
   | zmedico | that contains sets of packages pulled into a given slot.     |
   |         | This will make the data easier to analyze when implementing  |
   |         | a fix for bug #249185.                                       |

   | 12125   | Bug #249185 - For more useful output in cases when one or    |
   | zmedico | more USE deps trigger "SLOT conflicts", show the specific    |
   |         | atoms that triggered the conflict. TODO: Distiguish between  |
   |         | various possible causes and tailor messages to suit them.    |

   | 12126   | Fix inconsistencies between the "clean" and "cleanrm"        |
   | zmedico | phases.                                                      |

svn path=/main/branches/prefix/; revision=12133