Merged from trunk 8051:8058

   Merged from trunk 8051:8058

   | 8052    | Split USE evaluation code out of binarytree.inject() so that |
   | zmedico | it can be reused in populate().                              |

   | 8053    | Sync code between binarytree.inject() and populate().        |
   | zmedico |                                                              |

   | 8054    | Pass default package metadata values into the PackageIndex   |
   | zmedico | constructor for optional things like EAPI and SLOT.          |

   | 8055    | Pass into the PackageIndex constructor a list of package     |
   | zmedico | metadata keys that inherit a default value from the header.  |

   | 8058    | Use writemsg() to send exception string to stderr.           |
   | zmedico |                                                              |

svn path=/main/branches/prefix/; revision=8077