Merged from trunk 8186:8199

   Merged from trunk 8186:8199

   | 8187    | Allow the depgraph to add old-style virtual providers but    |
   | zmedico | prefer any pre-existing providers over new ones that are     |
   |         | added.                                                       |

   | 8188    | Use a simple Package class to bundle package data for        |
   | zmedico | depgraph.create() calls.                                     |

   | 8189    | Split the masked packages display out of                     |
   | zmedico | depgraph.select_dep().                                       |

   | 8190    | Split the package selection logic out of                     |
   | zmedico | depgraph.select_dep().                                       |

   | 8191    | Split the atom selection logic out of depgraph.select_dep(). |
   | zmedico |                                                              |

   | 8192    | Rename variable for consistency.                             |
   | zmedico |                                                              |

   | 8193    | Raise an InvalidDependString exception if necessary when the |
   | zmedico | depgraph is populating the filtered repo so that we don't    |
   |         | have to check the return value.                              |

   | 8194    | Make depgraph.xcreate() use the filtered repo to determine   |
   | zmedico | availablility of system/world atoms so that the              |
   |         | raise_on_missing parameter can be removed from               |
   |         | depgraph.select_dep().                                       |

   | 8195    | Bug #196537 - Make portageq check that the parameter is an   |
   | zmedico | existing directory and exit gracefully if not.               |

   | 8197    | Split the "arg" parameter out of depgraph.select_dep() so    |
   | zmedico | that it's used purely for processing atoms that are pulled   |
   |         | in by parent packages.                                       |

   | 8198    | Use a "depth" parameter to track depth of recursion relative |
   | zmedico | to the nearest argument atom.                                |

   | 8199    | Remove uneeded "arg" and "addme" parameters where possible.  |
   | zmedico |                                                              |

svn path=/main/branches/prefix/; revision=8212