[krbdev.mit.edu #1847] daemon.c doesn't build on tru64 unix

[Ken Raeburn via RT]

After the fix to 1791 re-enabled the building of the function 'daemon',
the builds on tru64 unix started failing because it won't compile
there.  (Previously, the nightly tests weren't running on the trunk for
alpha-osf; presumably the builds would have failed because 'daemon'
wasn't defined.)  The compiler complains about the usage of setpgrp with
no arguments when two are required.