Adjust configuration-files GUC behavior as per my recent proposal.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: 337ffcddbae15a3bde25b17dbb8a0832c597003f
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2004-10-09T23:13:22Z
Releases: 8.0.0
Adjust configuration-files GUC behavior as per my recent proposal.
The vars are renamed to data_directory, config_file, hba_file, and
ident_file, and are guaranteed to be set to accurate absolute paths
during postmaster startup.
This commit does not yet do anything about hiding path values from
non-superusers.

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