Merged from trunk 6815:6833

   Merged from trunk 6815:6833

   +------------------------------------------------------------------------+
   | 6816    | Always return a dict from dblink.getcontents() since callers |
   | zmedico | never expect to get None.                                    |
   |---------+--------------------------------------------------------------|
   | 6818    | Remove some useless dircache code.                           |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6821    | Reuse previously acquired lstat results.                     |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6823    | Cache dblink instances for security checks and reference     |
   | zmedico | counts during merge/unmerge so that each CONTENTS only has   |
   |         | to be parsed once. These can also be reused for              |
   |         | collision-protect.                                           |
   |---------+--------------------------------------------------------------|
   | 6825    | Use cached dblink instances for collision-protect.           |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6827    | Fix dblink.isowner() so it works properly when ROOT!=/.      |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6829    | For bug #134620, add a FEATURES=unmerge-orphans option that  |
   | zmedico | causes unmerge to remove files more aggressively. If a file  |
   |         | is not claimed by another package in the same slot and it is |
   |         | not protected by CONFIG_PROTECT, unmerge it even if the      |
   |         | modification time or checksum differs from the file that was |
   |         | originally installed. This is enabled in make.globals since  |
   |         | the vast majority of users probably want this.               |
   |---------+--------------------------------------------------------------|
   | 6831    | Add a note about the new unmerge-orphans behavior.           |
   | zmedico |                                                              |
   |---------+--------------------------------------------------------------|
   | 6833    | In dblink.treewalk(), handle the case where the current cpv  |
   | zmedico | is already installed but it has a different slot (multislot  |
   |         | or unapplied slotmove).                                      |
   +------------------------------------------------------------------------+

svn path=/main/branches/prefix/; revision=6940