Copy South Sudan rows using ISO codes

geocoder/admin0/patches/20180306_add_ssd_rows_for_south_sudan.sql

@@ -0,0 +1 @@
+insert into admin0_synonyms (name, rank, adm0_a3, name_) select name, rank, 'SSD' as adm0_a3, name_ from admin0_synonyms where adm0_a3 = 'SDS';