pgsql: Allow NOTIFY/LISTEN/UNLISTEN to only take relation names, not

Log Message:
-----------
Allow NOTIFY/LISTEN/UNLISTEN to only take relation names, not
schema.relation, because the notify code only honors the relation name.
schema.relation will now generate a syntax error.

Modified Files:
--------------
pgsql/src/backend/parser:
gram.y (r2.585 -> r2.586)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.585&r2=2.586)