BUG #4191: Include hint for Windows-like locals in documentation

The following bug has been logged online:

Bug reference:      4191
Logged by:          Martin Saschek
Email address:      m.saschek@automationwr.de
PostgreSQL version: 8.2.7; 8.3.1
Operating system:   Windows XP
Description:        Include hint for Windows-like locals in documentation
Details:

include a hint on the Windows-like encoding of locale settings in "Chapter
21. Localization".

Only by chance and after several hours (!) I found out that on Windows I
should use "German_Germany" rather than "de_DE".