pgsql: Use qualified_name instead of relation_expr for commands that

Log Message:
-----------
Use qualified_name instead of relation_expr for commands that have no
business with inheritance recursion: ALTER INDEX, ALTER SEQUENCE, ALTER
TRIGGER, ALTER VIEW. They would just silently ignore the ONLY.

ALTER TABLE has mixed behavior and cannot be dealt with this way because
of the resulting shift/reduce conflicts.

Modified Files:
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pgsql/src/backend/parser:
gram.y (r2.653 -> r2.654)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.653&r2=2.654)