Merged from trunk 8036:8043

   Merged from trunk 8036:8043

   | 8037    | Refactor depgraph.select_dep() to eliminate redundant code   |
   | zmedico | that was duplicated for each package type.                   |

   | 8038    | Comment about avoiding expensive metadata pulls in           |
   | zmedico | depgraph.select_dep().                                       |

   | 8039    | Prevent bogus upgrade display when a new-style virtual is    |
   | zmedico | first installed and it replaces an old-style virtual.        |

   | 8040    | Remove ambiguous "you should edit this file" warning. Thanks |
   | zmedico | to Cardoe.                                                   |

   | 8041    | Make portdbapi and bindbapi cache PROVIDE in order to        |
   | zmedico | optimize matching of old-style virtuals.                     |

   | 8042    | Move some package selection code from depgraph.create() to   |
   | zmedico | select_dep() so that all package selection is done in the    |
   |         | same place.                                                  |

   | 8043    | Raise a PackageNotFound exception instead of a ValueError in |
   | zmedico | order to avoid ambiguity if an unexpected ValueError occurs. |

svn path=/main/branches/prefix/; revision=8075