Merged from trunk 5414:5425

Merged from trunk 5414:5425

keep things quiet when uninstalling (SoLudd)

Send stuff that's not a warning or error to stdout rather than stderr.

fixup style (SpankMan)

detect incorrect absolute symlinks in libdirs (SpankMan)

For bug #159360, make sure that the highest available new-style virtual is
selected even if it has depes that aren't already installed.

Sort the --info USE flags for bug #159161.

Be slightly more defensive when loading the vdb/blockers caches.

Improve the logic for bug #159360 to ensure that an actual upgrade is selected
without any downgrades.

Do some small fixes to prevent slot collision nodes from interfering with the
depgraph.

Fix 'TypeError: unpack non-sequence' that occurs if myparent is None.

Punt the abort_unpack() handler since it's pointless anyway.

svn path=/main/branches/prefix/; revision=5427