[geonames] generated postal code TSV fields

src/postal_fields.h

@@ -0,0 +1,9 @@
+enum gn_postal_fields {
+    GN_POSTAL_CODE=0,
+    GN_POSTAL_COUNTRY_CODE=1,
+    GN_POSTAL_CONTAINING_GEONAME_ID=2,
+    GN_POSTAL_ADMIN1_IDS=3,
+    GN_POSTAL_ADMIN2_IDS=4,
+    GN_POSTAL_ADMIN3_IDS=5,
+    NUM_POSTAL_FIELDS
+};