simplify token precomputation

Rename function to reflect that it is only used for precomputation.
The token IDs are not really needed, so don't bother to compute
the array of tokens.

test/python/test_tools_database_import.py

@@ -187,7 +187,7 @@ def test_truncate_database_tables(temp_db_conn, temp_db_cursor, table_factory):
 @pytest.mark.parametrize("threads", (1, 5))
 def test_load_data(dsn, src_dir, place_row, placex_table, osmline_table, word_table,
                    temp_db_cursor, threads):
-    for func in ('make_keywords', 'getorcreate_housenumber_id', 'make_standard_name'):
+    for func in ('precompute_words', 'getorcreate_housenumber_id', 'make_standard_name'):
         temp_db_cursor.execute("""CREATE FUNCTION {} (src TEXT)
                                   RETURNS TEXT AS $$ SELECT 'a'::TEXT $$ LANGUAGE SQL
                                """.format(func))