Reenable database ramcache and playlist dircache

Playlist dircache references should be back in working order.

Reenabling dircache references in the database ramcache is not
yet done as it requires quite a bit of rework. Otherwise, the
database in RAM is functional again.

Some buffer compatibility changes have been made for database
commit because the dircache buffer can no longer be stolen, only
freed by an API call.

Change-Id: Ib57c3e98cb23e798d4439e9da7ebd73826e733a4
4 files changed