support latest MiniJSON

I corrected about the code of the part depending on MiniJSON, and supported latest MiniJSON. :)

Latest MiniJSON code is here.
https://gist.github.com/darktable/1411710/d7c8c5fd25d86031e52883f4e69c31234b5e735c
https://gist.github.com/darktable/1411710