Improved tab completion for views with triggers.

Improved tab completion for views with triggers.

Allow INSERT INTO, UPDATE, and DELETE FROM to be completed with
either the name of a table (as before) or the name of a view with
an appropriate INSTEAD OF rule.

Along the way, allow CREATE TRIGGER to be completed with INSTEAD OF,
as well as BEFORE and AFTER.

David Fetter, reviewed by Itagaki Takahiro