BUG #6077: documentation on PQfmod for numeric data types

The following bug has been logged online:

Bug reference: 6077
Logged by: Dmitry Grebeniuk
Email address: gdsfh1(at)gmail(dot)com
PostgreSQL version: 9.1beta2
Operating system: any; documentation issue
Description: documentation on PQfmod for numeric data types
Details:

> The interpretation of modifier values
> is type-specific; they typically indicate
> precision or size limits.

This documentation on PQfmod doesn't help when one tries to determine the
scale/precision of column with numeric data type. Please add more specific
documentation or any links to documentation about "type-specific
interpretation". (documentation on numeric data types, chapter 8.1, was
grepped for substring "fmod" and "modi" without any results.)