pg_ls_dir & friends still have a hard-coded superuser check

Commit 1574783b4ced0356fbc626af1a1a469faa6b41e1 gratifyingly removed
hard-coded superuser checks from assorted functions, which makes it
possible to GRANT EXECUTE ON FUNCTION pg_catalog.whatever() to
unprivileged users if the DBA so desires. However, the functions in
genfile.c still have hard-coded checks: pg_read_file(),
pg_read_binary_file(), pg_stat_file(), and pg_ls_dir(). I think those
functions ought to get the same treatment that the commit mentioned
above gave to a bunch of others. Obviously, there's some risk of DBAs
doing stupid things there, but stupidity is hard to prevent in a
general way and nanny-ism is annoying. The use case I have in mind is
a monitoring tool that needs access to one more of those functions --
in keeping with the principle of least privilege, it's much better to
give the monitoring user only the privileges which it actually needs
than to make it a superuser.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company