pgsql-server: Clarify schema meanings in pg_dump manual page by

Log Message:
-----------
Clarify schema meanings in pg_dump manual page by referring to object
definitions more frequently.

Modified Files:
--------------
pgsql-server/doc/src/sgml/ref:
pg_dump.sgml (r1.71 -> r1.72)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/ref/pg_dump.sgml.diff?r1=1.71&r2=1.72)