Another interesting check might be that maybe there should be an error
   if FDSCRIPTS is set and FDESCFS isn't, since you certainly can't pass
   a valid /dev/fd/N if you don't have FDESCFS.

That's not true.  `MAKEDEV std' creates a /dev/fd populated with device
nodes that sort-of do the right thing.  FDESC is better, but optional.


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