Also, don't allow setting reloptions on them, since that would have no
effect given the lack of storage.  The patch does this by introducing
a new reloption kind for which there are currently no reloptions -- we
might have some in the future -- so it adjusts parseRelOptions to
handle that case correctly.

Bumped catversion.  System catalogs that contained reloptions for
partitioned tables are no longer valid; plus, there are now fewer
physical files on disk, which is not technically a catalog change but
still a good reason to re-initdb.

Amit Langote, reviewed by Maksim Milyutin and Kyotaro Horiguchi and
revised a bit by me.

Discussion: http://postgr.es/m/20170331.173326.212311140.horiguchi.kyotaro@lab.ntt.co.jp