Log Message:
-----------
Add a note to the docs describing NaN's equality and ordering behavior.
Per recent -hackers thread, this is noteworthy because Postgres behaves
differently from most implementations of NaN, including IEEE754.
Modified Files:
--------------
pgsql/doc/src/sgml:
datatype.sgml (r1.183 -> r1.184)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml.diff?r1=1.183&r2=1.184)