control/event.c: Make detach-ing from an event safe: A detached callback can't be called after event_detached. Add an internal event_detach_lock_state, to bypass this feature.

and install facility for text scaling similar to freetype.c.

xspf-specs seems to agree that it's valid this way. (title tag MAY
appear once in item)

playlist/items.c: Add a left over that might prevent art/meta from being fetched. Reported by ileoo.

- always round Scale to 1 because we only support that value