TODO file:
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* Support abstract MTP album (0xBA03) just like playlists. Too
  bad that Creative devices do not support them, they group the
  albums by using the metadata instead.

* Support playback and volume setting on devices that have it.
  (I don't have one - Linus.)

* Add logic to transfer very large files in chunks, like 1 MB at the
  time, or we cannot upload movies... Righ now libmtp just copy the
  file to memory and transfer it.

* Previous fix can help to get the callbacks working again, cause
  right now they aren't called.

* Make the usb r/w stuff in libusb-glue.c take the device as parameter,
  then put the callback function in the device and make it call.
  (IMPOSSIBLE: the device is created after a lot of writing has already
   taken place, shall we use a dummy device holder then?)

* Fix compiler warnings.

* Make an API that can return several devices not just connect to the
  first one...

* Add a function that will list the playable file types for a certain 
  device. (Needs some research and probably a database.) Can the device
  be probed to determine supported file types?
