Commit 13208bf5a7 added range support to
the `move` command, but applied the wrong offset to the `to` variable.
When the source range is before the current song, and the song thus
gets decremented by the range size, then the final destination offset
must also be decremented by the range size.
Closes https://github.com/MusicPlayerDaemon/MPD/issues/663
12a86c4975