hdf5_der

[svn-r23606] add support for named datatypes in the IOD plugin:
 - H5Topen_ff is still implemented synchronously because the async
   implementation will be very ugly. It's better to think of a better way
   to implement asynchronously.

add a native backend to the server:
 - Enabling this enforces that create calls are independent for now,
   since we are not just printfing at the server anymore.