PATCH: More search in object's definitions

Hello!

This patch adds search capabilities for:

* Column's type names and default values
* Everything in a view definition
* Column names in composite types, tables and foreign tables

I'm not sure how far should this feature be developed further. Is it
enough to cover most typical needs? (with this patch I feel my needs
almost covered)
Or should it take a burden of revealing _each_and_every_ usage of
constants and object dependencies not managed by DBMS? In the latter
case we'd firstly make up a list of these.

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Best regards,
 J.F.