Local partitioned indexes and pageinspect

It looks like local partitioned indexes are a problem for pageinspect:

pg@regression[28736]=# select bt_metap('at_partitioned_b_idx');
ERROR:  relation "at_partitioned_b_idx" is not a btree index

I gather that pageinspect simply didn't get the memo about the new
RELKIND_PARTITIONED_INDEX "placeholder" relkind. I think that it
should at least give a friendlier error message than what we see here.
The same applies to amcheck, and possibly a few other modules.

I also noticed that the new 'I' relkind is not documented within the
pg_class docs. I think that that needs to be updated. The docs should
explain that 'I' relations are not backed by storage, since that will
probably affect users of one or two external tools.

-- 
Peter Geoghegan