Merged from trunk 5165:5171

Merged from trunk 5165:5171

When portdbapi.aux_get() generates a KeyError in
portage.getmaskingstatus(), handle it by reporting "corruption".

Make `repoman fix` work with the new ebuild Manifest checks during
depend phase.

Update the RESTRICT=binchecks docs.  Thanks to jakub for the suggestion
and antarus for the patch.

For `ebuild --force digest`, exempt the depend phase from Manifest
checks.

Use portage.chdir() instead of os.chdir() in order to avoid an 'OSError:
[Errno 2] No such file or directory' if the working directory doesn't
exist.  Thanks to Caster for reporting.

svn path=/main/branches/prefix/; revision=5172