Support SQLite INDEXED BY and NOT INDEXED

Examples:
  (from (src :t (not-indexed))) => FROM t NOT INDEXED
  (from (src :t (indexed-by :ix))) => FROM t INDEXED BY ix

  (from :t1 (join :tbl2 (as :t2) (indexed-by :ix) (using :pk))) =>
  FROM t1 JOIN tbl2 AS t2 INDEXED BY ix USING(pk)