- Explicitly forbids opclass, collation and indoptions (like DESC/ASC etc) for
  including columns. Throw an error if user points that.
- Truncated storage arrays for such attributes to store only key atrributes,
  added assertion checks.
- Do not check opfamily and collation for including columns in
  CompareIndexInfo()

Discussion: https://www.postgresql.org/message-id/5ee72852-3c4e-ee35-e2ed-c1d053d45c08@sigaev.ru