Merged from trunk 9894:9906

   Merged from trunk 9894:9906

   | 9895    | Fix issues with an empty string being passed into            |
   | zmedico | PreservedLibsRegistry.register() now that COUNTER is not     |
   |         | loaded via config.load_infodir(). Thanks to grobian for      |
   |         | reporting.                                                   |

   | 9896    | In config.setcpv() and regenerate(), replace                 |
   | zmedico | str.startswith() calls with slice comparison. It's not       |
   |         | pretty but performance is critical in this section of code   |
   |         | and there is a measurable performance difference.            |

   | 9898    | Bug #217664 - Fix emerge 'by path' package argument handling |
   | zmedico | so that Package instances are properly cached (avoiding a    |
   |         | KeyError later).                                             |

   | 9900    | Revert part of atom selection consistency improvement from   |
   | zmedico | r9873 since it in some cases it triggers unresolvable direct |
   |         | circular dependencies. For example, this happens with        |
   |         | gwydion-dylan which depends on either itself or              |
   |         | gwydion-dylan-bin. In case gwydion-dylan is not yet          |
   |         | installed, gwydion-dylan-bin needs to be selected in order   |
   |         | to avoid a an unresolvable direct circular dependency.       |

   | 9901    | Add support to depgraph._select_atoms() to take a "parent"   |
   | zmedico | parameter and use that to try and avoid unresolvable direct  |
   |         | circular dependencies when necessary. Also, make atom        |
   |         | selection more consistent with the graph to solve some cases |
   |         | of bug #1343. This improves the fix from bug #141118 to work |
   |         | in cases when a virtual is not yet installed but it has been |
   |         | pulled into the graph. For example, see the case of in Bug   |
   |         | #163801#c17, where we want kaffe to satisfy virtual/jdk-1.4  |
   |         | without an extra jvm being pulled in unnecessarily.          |

   | 9904    | Comment some more on the significance of passing the         |
   | zmedico | graph_db and parent into depgraph._select_atoms() to solve   |
   |         | some cases of bug #1343 while avoiding unresolvable direct   |
   |         | circular dependencies.                                       |

   | 9906    | The dependency resolver now has a feedback mechanism that    |
   | zmedico | helps make atom selections more consistent with previous     |
   |         | selections that have been added to the graph. This solves    |
   |         | some common cases of bug #1343.                              |

svn path=/main/branches/prefix/; revision=9909