pgsql: Correct documentation error: in 8.1 and 8.2, %p in archive and

Log Message:
-----------
Correct documentation error: in 8.1 and 8.2, %p in archive and restore
command strings inserts relative not absolute path of file to process.
This is a side-effect of 2005-07-04 change that makes the server use
relative paths in general.  Noted by Bernd Helmle.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        backup.sgml (r2.92 -> r2.93)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/backup.sgml.diff?r1=2.92&r2=2.93)
        config.sgml (r1.92 -> r1.93)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml.diff?r1=1.92&r2=1.93)