Merged from trunk -r13690:13696

   Merged from trunk -r13690:13696

   | 13691   | * Add a Package.invalid attribute to store messages about    |
   | zmedico | invalid LICENSE, PROPERTIES, PROVIDE, and RESTRICT metadata. |
   |         | Use it to mask invalid packages when necessary. * Evaluate   |
   |         | USE conditional values in Package.metadata when the are      |
   |         | accessed.                                                    |

   | 13692   | Add a Package.metadata.properties attribute containing a     |
   | zmedico | list of enabled PROPERTIES values.                           |

   | 13693   | Add a Package.metadata.restrict attribute containing a list  |
   | zmedico | of enabled RESTRICT values.                                  |

   | 13694   | Make config.regenerate() detect api-level updates to         |
   | zmedico | ACCEPT_LICENSE, for use in implementing the "free" filter    |
   |         | for the packagekit backend.                                  |

   | 13695   | Make dbapi.cp_list() raise NotImplementedError.              |
   | zmedico |                                                              |

   | 13696   | Use @property instead of __getattribute__ to implement lazy  |
   | zmedico | Package.iuse.regex initialization.                           |

svn path=/main/branches/prefix/; revision=13718