For Android pre-5.0 compatibility (#213).

Declare two named elements.  An enum should not be used as an array
index, as this is error prone.

Move code from the Vorbis and FLAC decoder plugins.

Avoid reversing the order after every update.

False if the vector was not modified.

Don't open the music directory for each "lsinfo" call.  Get the list
of playlist files from the memory database.