UNSIGNED48 is not working

[nattgris]

Unfortunately it seems there is no way to use objects of datatype UNSIGNED48, or any other INTEGER or UNSIGNED of size between 32 and 64.

Even for 64 bit integers, there's no way to programmatically handle the access via a co_access_fn.

UNSIGNED48 is widely used for all virtual I/O in e.g. CiA 417, where programmatic access is also needed to take care of the somewhat complicated behaviour of those objects.