Revert "dblink.mergeme(): Merge files in alphabetic order."

This reverts commit 1d4ac47c28706094230cb2c4e6ee1c1c71629aa0.
As discussed on the gentoo-portage-dev mailing list, if we don't have
a compelling reason to sort here then it's just a waste:

http://archives.gentoo.org/gentoo-portage-dev/msg_67b08fcd7a1b832b347caf1b19362cbb.xml
diff --git a/pym/portage/dbapi/vartree.py b/pym/portage/dbapi/vartree.py
index 099164a..dd74c10 100644
--- a/pym/portage/dbapi/vartree.py
+++ b/pym/portage/dbapi/vartree.py
@@ -3981,7 +3981,7 @@
 			mergelist = stufftomerge
 			offset = ""
 
-		for i, x in enumerate(sorted(mergelist)):
+		for i, x in enumerate(mergelist):
 
 			mysrc = join(srcroot, offset, x)
 			mydest = join(destroot, offset, x)