Merged from trunk 8435:8447

   Merged from trunk 8435:8447

   | 8436      | Allow multislot packages to be added to the world file via |
   | zmedico   | --noreplace. Having these atoms in the world file will     |
   |           | trigger recommendations to run emaint in some cases, like  |
   |           | when running `emerge -e world`. The atoms need to be in    |
   |           | the world file to prevent multislot packages from being    |
   |           | removed by --depclean though.                              |

   | 8437      | remove O and PPID from being readonly. O is set python     |
   | WarnerBro | side (and we will hopefully stop being exported soon. PPID |
   |           | is ro by bash, so no need to declare it twice              |

   | 8438      | Bug #198129 - Prevent SLOT atoms like sys-devel/binutils:0 |
   | zmedico   | from being inappropriately recorded in the world file when |
   |           | USE=multislot is enabled.                                  |

   | 8439      | Fix create_world_atom() logic some more for bug #198129.   |
   | zmedico   |                                                            |

   | 8442      | Go ahead and exempt selected profile-specific USE_EXPAND   |
   | zmedico   | flags from IUSE QA Notices since we are planning to make   |
   |           | these particular flags into implicit members of IUSE. We   |
   |           | can make this extensible later, but for now we just want   |
   |           | to eliminate some useless QA Notices (a subset of bug      |
   |           | #70648). We're not exempting any non profile- specific     |
   |           | USE_EXPAND flags here. For non profile-specific flags, we  |
   |           | intend to implement an IUSE syntax extension (bug          |
   |           | #133327).                                                  |

   | 8444      | Remove references to ${O} in dyn_spec() since antarus made |
   | zmedico   | that variable mutable.                                     |

   | 8445      | Simplify and fix bugs in is_valid_package_atom().          |
   | zmedico   |                                                            |

   | 8447      | Remove the usage.obsolete "KEYWORDS contain -*" warning    |
   | zmedico   | since people are using -* to indicate that a package       |
   |           | should not be tried on archs other than those for which it |
   |           | already has KEYWORDS.                                      |

svn path=/main/branches/prefix/; revision=8449