Re: three small improvements for "Composite Types" page

Hello,

While reading "Composite Types" manual page I've noticed that it is
somewhat hard to follow by trying out given examples. I suggest three
small changes which would make this page a little easier to follow for
me:

1. Clarify "different kind" by adding a link to a section of "create
type" page

 > Note that the AS keyword is essential; without it, the system will
think a different kind of CREATE TYPE command is meant, and you will get
odd syntax errors.

Here there is no link to CREATE TYPE, so it's not so easy to go there to
see what is that "different kind" of CREATE TYPE. I suggest to add an
anchor for the "Base Types" section there and link the words "different
kind" there.

 > The syntax is comparable to CREATE TABLE, except ...

It would be useful if this CREATE TABLE (first on this page) would
become a link.

3. Simplify CREATE TABLE example to make it self-sufficient

One of the examples on the same "Composite Types" page is an example of
CREATE TABLE:

CREATE TABLE inventory_item (
     name            text,
     supplier_id     integer REFERENCES suppliers,
     price           numeric CHECK (price > 0)
);

This example is not self-sufficient: it requires one to have "suppliers"
table with specific column to work as given.