BUG #15356: Inconsistent documentation about CREATE TYPE

The following bug has been logged on the website:

Bug reference:      15356
Logged by:          Lukas Eder
Email address:      lukas.eder@gmail.com
PostgreSQL version: 10.5
Operating system:   Windows
Description:

Hello,

The CREATE TYPE documentation [1] specifies that enum types without any enum
labels are possible:

    CREATE TYPE name AS ENUM ( [ 'label' [, ... ] ] )

I can confirm this. The following statement works well:

    CREATE TYPE e AS ENUM ();

However, further down in the same documentation page, we can see:

    "Enum types take a list of one or more quoted labels"

It should read "zero or more quoted labels". I suspect this should be
adapted on all documentation pages from PostgreSQL 9.0 onwards. In 8.4, the
documentation was consistent [2]

[1]: https://www.postgresql.org/docs/current/static/sql-createtype.html
[2]: https://www.postgresql.org/docs/8.4/static/sql-createtype.html