Merged from trunk -r14274:14284

   Merged from trunk -r14274:14284

   | 14279   | Atom optimizations. Remove the metaclass and cache since it  |
   | zmedico | just slows it down. Thanks to Marat Radchenko                |
   |         | <marat@slonopotamus.org> for this patch.                     |

   | 14280   | Use a dict for Package.metadata, because it's faster. Thanks |
   | zmedico | to Marat Radchenko <marat@slonopotamus.org> for this patch   |
   |         | from bug #276813.                                            |

   | 14281   | Fix _expand_new_virtuals() to preserve USE deps in atoms for |
   | zmedico | new-style virtuals, and update the corresponding depgraph    |
   |         | code.                                                        |

   | 14282   | Avoid lots of redundant Atom constructor calls. Thanks to    |
   | zmedico | Marat Radchenko <marat@slonopotamus.org> for the initial     |
   |         | patch from bug #276813.                                      |

   | 14283   | Remove obsolete InvalidAtom handler in                       |
   | zmedico | _add_pkg_dep_string().                                       |

   | 14284   | Revert accidental changes                                    |
   | zmedico | _unicode_module_wrapper.__getattribute__ from previous       |
   |         | commit.                                                      |

svn path=/main/branches/prefix/; revision=14332