EXT-8524 FIXED Non-ASCII character corruption in date.

Convert formatted date from system charset to UTF-8 on Windows (other OSes don't require this).

See http://jira.secondlife.com/browse/EXT-8318 for more details.

Reviewed by Sergey Litovchuk at https://codereview.productengine.com/secondlife/r/834/

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branch : product-engine