pgsql: Some small docs improvements motivated by reading the comments

Log Message:
-----------
Some small docs improvements motivated by reading the comments for the 7.4
7.4 interactive docs.

Modified Files:
--------------
pgsql/doc/src/sgml:
datatype.sgml (r1.152 -> r1.153)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml.diff?r1=1.152&r2=1.153)
func.sgml (r1.232 -> r1.233)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.232&r2=1.233)