pgsql: Fix potentially-unportable code in contrib/adminpack.

Fix potentially-unportable code in contrib/adminpack.

Spelling access(2)'s second argument as "2" is just horrid.
POSIX makes no promises as to the numeric values of W_OK and related
macros.  Even if it accidentally works as intended on every supported
platform, it's still unreadable and inconsistent with adjacent code.

In passing, don't spell "NULL" as "0" either.  Yes, that's legal C;
no, it's not project style.

Back-patch, just in case the unportability is real and not theoretical.
(Most likely, even if a platform had different bit assignments for
access()'s modes, there'd not be an observable behavior difference
here; but I'm being paranoid today.)

Branch
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REL9_5_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/f29eff7ac500e5d75a3c1991ba0a4fa09946e6b7

Modified Files
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contrib/adminpack/adminpack.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)