Introduce VSS_NEW_AUDIO_FILE to fix playlist updates.

Introduce VSS_NEW_AUDIO_FILE to fix playlist updates.

The playlist event handler handles afsi change events by moving the affected
entry to the end of the playlist. This is the right thing to do if the
event was triggered by virtual streaming system streaming a new file. It is
incorrect, however, if the event was triggered by a subcommand such as touch.

This commit introduces the new afs event type VSS_NEW_AUDIO_FILE to distinguish
between the two different use cases. The audio file table event handler
ignores the VSS_NEW_AUDIO_FILE event while the playlist event handler ignores
the AFSI_CHANGE event. The moods event handler treats both events equally,

Get rid of a pointless static one-liner function in playlist.c while at it.