config: unset LINGUAS if appropriate, bug #459350
Display: eliminate duplicate vardb.match() calls
Display: unsplit _display_use method parts
_display_use: use local variables
portage(5): document multiple parents in the parent file

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Fix autounmask/sub-slot interference, bug #459832
depgraph._set_args: fix atom_arg_map for refs > 1

Due to an indentation error, atom_arg_map only preserved a single
set reference, preventing slot-operator rebuilds from triggering
for atoms that were also pulled in via another set such as world.
repoman: check metadata.xml doctype, bug #328113
repoman: remove unused grouplist function