BUG #14016: Incomplete documentation of IN subquery expression

The following bug has been logged on the website:

Bug reference: 14016
Logged by: Manlio Perillo
Email address: manlio(dot)perillo(at)gmail(dot)com
PostgreSQL version: 9.5.1
Operating system: Linux
Description:

At the end of the documentation for VALUE (sql-values.html), there is the
following tip:
"For simple IN tests, it's better to rely on the list-of-scalars form of IN
than to write a VALUES query as shown above"

However there is no reference to the "list-of-scalars" forms of IN, in the
functions-subquery.html page. It is only reported that the supported syntax
is "expression IN (subquery)"

The reference was available in an old version (7.3), where the manual
documented both the scalar form and sub query form:
"expression IN (value[, ...])"