Log Message:
-----------
Improve documentation for COALESCE and NULLIF. Add references for NVL
and IFNULL.
Backpatch to 8.1.X.
Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.295 -> r1.296)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.295&r2=1.296)