[Proposal] Adjust the signatures of the netfs_make_protid and netfs_make_peropen functions to match those of diskfs_create_protid and diskfs_make_peropen.

[Mikhail Karpov]

Hello,

Currently, there are several places in the GNU/Hurd codebase where the 
return
values ​​of the functions netfs_make_protid and netfs_make_peropen are not
checked.  While it would be straightforward to add these checks by verifying
whether the returned pointer is NULL a potentially better solution would be
to adjust the signatures of these functions to match those of
diskfs_create_protid and diskfs_make_peropen.  In that case, we would simply
need to ensure that the functions do not return any errors.  This would also
reduce the divergence in the code between libnetfs and libdiskfs.
Thanks,

--
Mikhail Karpov