Log Message:
-----------
Fix inheritance description to note that not-null constraints are
inherited, per Taiki Yamaguchi.
Modified Files:
--------------
pgsql/doc/src/sgml:
ddl.sgml (r1.68 -> r1.69)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ddl.sgml.diff?r1=1.68&r2=1.69)