Revisit all buffer_out parameters

[Burgestrand]

Would be neat if spotify could make dealing with buffer_out parameters a little nicer. Perhaps wrapping the functions? There is only like two of them that do not have a clear better implementation.

• image_data
• link_as_string
• link_as_track_and_offset
• playlist_get_image
• playlistcontainer_playlist_folder_name
• session_create
• session_process_events
• session_remembered_user
• session_is_scrobbling
• session_is_scrobbling_possible

[Burgestrand]

Still have create_session left, but I'm not sure what to do with it considering the error return value is also of great importance.

[Burgestrand]

While I'm breaking backwards-compatibility, I might as well make all functions that previously returned an error, raise the error. In pretty much all cases that's what you want anyway?

[Burgestrand]

Here are some more functions that could get some sugar:

• playlist_add_tracks
• playlist_remove_tracks
• playlist_reorder_tracks
• playlistcontainer_get_unseen_tracks
• track_set_starred
• inbox_post_tracks (uses callbacks)