BUG(1852): Optimized the list handling in xmms_medialib_add_recursive().
BUG(1852): Optimized the list handling in xmms_medialib_add_recursive().

This change replaces a costly g_list_reverse() call by just adding an
list node which is later used to find the end of the list quickly.

mantaraya36/xmms2-mantaraya36,theeternalsw0rd/xmms2,mantaraya36/xmms2-mantaraya36,theeternalsw0rd/xmms2,mantaraya36/xmms2-mantaraya36,krad-radio/xmms2-krad,theeternalsw0rd/xmms2,chrippa/xmms2,xmms2/xmms2-stable,oneman/xmms2-oneman-old,krad-radio/xmms2-krad,dreamerc/xmms2,chrippa/xmms2,theefer/xmms2,dreamerc/xmms2,oneman/xmms2-oneman-old,krad-radio/xmms2-krad,mantaraya36/xmms2-mantaraya36,mantaraya36/xmms2-mantaraya36,theefer/xmms2,oneman/xmms2-oneman,chrippa/xmms2,xmms2/xmms2-stable,krad-radio/xmms2-krad,six600110/xmms2,theefer/xmms2,xmms2/xmms2-stable,six600110/xmms2,theefer/xmms2,oneman/xmms2-oneman-old,dreamerc/xmms2,oneman/xmms2-oneman-old,krad-radio/xmms2-krad,dreamerc/xmms2,six600110/xmms2,xmms2/xmms2-stable,oneman/xmms2-oneman,krad-radio/xmms2-krad,chrippa/xmms2,oneman/xmms2-oneman,theeternalsw0rd/xmms2,chrippa/xmms2,theefer/xmms2,theeternalsw0rd/xmms2,theefer/xmms2,theefer/xmms2,oneman/xmms2-oneman,six600110/xmms2,dreamerc/xmms2,mantaraya36/xmms2-mantaraya36,oneman/xmms2-oneman,oneman/xmms2-oneman,theeternalsw0rd/xmms2,oneman/xmms2-oneman-old,six600110/xmms2,oneman/xmms2-oneman,six600110/xmms2,chrippa/xmms2,xmms2/xmms2-stable,mantaraya36/xmms2-mantaraya36,xmms2/xmms2-stable