Make all topics visible in ToCs

Every topic in our documentation set appears in the table of contents for its manual, except for four syntax-related topics in the Reference Manual:

• column-definition, generated-column-spec, and generation-clause, all under the CREATE TABLE statement

• ReferencingClause, under the CREATE TRIGGER statement

All of these have the following attribute setting in the map file:

toc="no"

I'd like to remove this setting for the following reasons:

• The documentation for all other syntax clauses can be found in the ToC.

• Except for ReferencingClause, all are linked to from other topics in addition to their parent topic.

• I have often been puzzled that I can get to those topics by clicking links but not by locating them in the ToC. (I may spend more time navigating the Reference Manual than most people do, of course.)

Unless someone can provide a reason why these topics in particular should be hidden, I'll file a patch soon and commit it in a day or two.

Although this situation has existed since 10.1, I don't plan to backport the fix, since it's a very minor issue.