emerge: support ../ path arguments

This will fix bug #354141.
diff --git a/pym/_emerge/depgraph.py b/pym/_emerge/depgraph.py
index c4d84ab..245e38e 100644
--- a/pym/_emerge/depgraph.py
+++ b/pym/_emerge/depgraph.py
@@ -1621,7 +1621,8 @@
 				# Queue these up since it's most efficient to handle
 				# multiple files in a single iter_owners() call.
 				lookup_owners.append(x)
-			elif x.startswith("." + os.path.sep):
+			elif x.startswith("." + os.sep) or \
+				x.startswith(".." + os.sep):
 				f = os.path.abspath(x)
 				if not f.startswith(myroot):
 					portage.writemsg(("\n\n!!! '%s' (resolved from '%s') does not start with" + \