pgsql: Properly document return value of strpos().

Log Message:
-----------
Properly document return value of strpos().

Tags:
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REL8_1_STABLE

Modified Files:
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pgsql/doc/src/sgml:
func.sgml (r1.291 -> r1.291.2.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.291&r2=1.291.2.1)
pgsql/src/tools/fsync:
README (r1.2 -> r1.2.6.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/fsync/README.diff?r1=1.2&r2=1.2.6.1)
test_fsync.c (r1.11.2.1 -> r1.11.2.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/fsync/test_fsync.c.diff?r1=1.11.2.1&r2=1.11.2.2)