Merged from trunk 6338:6344

   Merged from trunk 6338:6344
   (Do the changes I did yesterday again, but then the right way)

   +------------------------------------------------------------------------+
   | 6339    | Punt the sorted_versions() function in favor of              |
   | zmedico | list.sort(vercmp).                                           |
   |---------+--------------------------------------------------------------|
   | 6341    | Don't set os.environ["USERLAND"] inside portage.data and     |
   | zmedico | rely on USERLAND from the profile instead (bail out if       |
   |         | necessary when USERLAND is unset).                           |
   |---------+--------------------------------------------------------------|
   | 6342    | Don't force OS detection in the portage.data module.         |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6343    | Make sure XARGS has a default value.                         |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6344    | Provide a default value to the getattr call.                 |
   | zmedico |                                                              |
   +------------------------------------------------------------------------+

svn path=/main/branches/prefix/; revision=6345