Re: documentation structure

>
> And it's very inconsistent. For example, some functions use <optional>
> tags for optional parameters, others use square brackets, and some use
> <literal>VARIADIC</literal> to indicate variadic parameters, others use
> ellipses (sometimes in <optional> tags or brackets).

Having just written a couple of those functions, I wasn't able to find any
guidance on how to document them with regards to <optional> vs [], etc.
Having such a thing would be helpful.

While we're throwing out ideas, does it make sense to have function
parameters and return values be things that can accept COMMENTs? Like so:

COMMENT ON FUNCTION function_name [ ( [ [ argmode ] [ argname ] argtype [,
...] ] ) ] ARGUMENT argname IS '....';
COMMENT ON FUNCTION function_name [ ( [ [ argmode ] [ argname ] argtype [,
...] ] ) ] RETURN VALUE IS '....';

I don't think this is a great idea, but if we're going to auto-generate
documentation then we've got to store the metadata somewhere, and
pg_proc.dat is already lacking relevant details.