I can't find the prototypes for eg trivfs_S_io_read

[Ulrich Eckhardt <doomster@knuut.de>]

Hi people!
I have been hacking an example-translator (based on the run-translator) which 
uses io_read and io_seek. While the run-translator gave me the needed 
prototypes for those two, I can't find something like a header on my whole 
system.
 I have gotten around to notice that these protos somehow stem from 
hurd/io.defs, but have not been able to extract them. When applying mig on 
this file, I do get io_read, but the parameters passed are not the same. In 
fact, some are the same and you can easily spot that those two are related, 
but I can't figure out what to do with the rest.

A few notes/questions that crossed my way:
- I would have looked for those prototypes in the hurd-dev package, to be 
exact in hurd/trivfs.h. Should I file a bug against this, is it a bug at all ?
Of course I have found the functions themselves in the hurd soruces, but 
shouldn't hurd-dev be enough for me ?
- invoking 'mig --help': there is a missing 'generates ' in the description
- It seems that my translator 'overrides' the functions from libtrivfs, just 
like with virtual functions in C++, right ? Is there also a way to call the 
function provided by libtrivfs from my overridden function (like calling 
Base::function() in C++)?
- what does the _S_ in the function-name mean ?

thank you
Uli