Always pass encodings='utf_8' to codecs.open(), since otherwise it can

Always pass encodings='utf_8' to codecs.open(), since otherwise it can
return non-unicode strings (at least in some cases, observed with
python-2.6.2). Don't use unicode in portage.util.getconfig() for now,
since shlex doesn't seem to support it (spurious \0 characters). If we
use unicode for config variables, it breaks shlex.split() calls on those
variables due to the same issue (spurious \0 characters).

svn path=/main/trunk/; revision=13845