Tab completion for ALTER MATERIALIZED VIEW ... SET ACCESS METHOD

Hello hackers,

SET ACCESS METHOD is supported in ALTER TABLE since the commit
b0483263dd. Since that time, this also has be allowed SET ACCESS
METHOD in ALTER MATERIALIZED VIEW. Although it is not documented,
this works.

I cannot found any reasons to prohibit SET ACCESS METHOD in ALTER
MATERIALIZED VIEW, so I think it is better to support this in psql
tab-completion and be documented.

I attached a patch to fix the tab-completion and the documentation
about this syntax. Also, I added description about SET TABLESPACE
syntax that would have been overlooked.

Regards,
Yugo Nagata

--
Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>