- Fix crash when calling add-next and cur_playing/cur_streaming are NULL
- Append songs after cur_streaming
Merge pull request #28 from chme/fixaddnext

Fix crash when calling add-next and cur_playing/cur_streaming are NULL
Change behavior of skip to previous song to start the current song from
the beginning, if it is playing for more than 3 seconds
local audio: do not add pcm_buf_threshold to pcm_pos (leads to wrong
position in Remote)