coverart: thread safety
Race conditions, pixbuf cache
Sort pixbuf cache for faster retrieval
Dynamic pixbuuf cache size
Use CAIRO_FILTER_BEST for default pixmap
gtkui: separate pixbuf caches for widget and playlist
dynamic callback list, never full
coverart: better handling of missing image file
Merge pull request #44 from Lithopsian/search

Coverart, thread safety, pixbuf cache