Factor out mdb_find_oldest,mdb_dlist_free,dirty_list.
Factor out mdb_find_oldest,mdb_dlist_free,dirty_list.

Do not rescan reader table (mdb_find_oldest) after "goto again".
Skip clearing dirty_list[nonzero].mid in mdb_dlist_free(); it
was not done in mdb_reset0() anyway.

bobek-balinek/BlueJet