pgsql: Clarify that locale names on Windows are more verbose.

Log Message:
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Clarify that locale names on Windows are more verbose.

Report from Martin Saschek

Modified Files:
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pgsql/doc/src/sgml:
charset.sgml (r2.85 -> r2.86)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/charset.sgml?r1=2.85&r2=2.86)